This is a list of businesses that can work for the right person, you may find something you can do or a few you're interested in or none at all.
Moving business, you need either an extended bed pickup truck or a box truck (if you have a pickup truck, that can be your only vehicle; but it gives lots of options for earning money.) You may need insurance, you may do the work yourself or hire people; $300 for a simple moving job is on the low end of prices.
Cleaning houses Maid services often have branded vehicles, but independent contractors often work as a team (group driving and pickup); usually a couple women will do cleaning as a team for safety. A small house can cost $1000 to clean, a small room can be $150 and take a couple hours. You'd have to check your local regulations if this is a business you'd want to be in, I don't know what kind of permits are involved and it goes without saying that a person should be an adult before being involved in a business that involves going into other people's homes. Someone with a knack for cleaning could easily make a few hundred a day, I think most of them just advertise on Facebook Marketplace. It can involve noxious chemicals used for cleaning, doing that a lot is potentially a health risk so I don't encourage it and only list it for a broad list of options.
Lawn mowing, this used to be a job for a neighborhood kid; but they don't seem to be the ones mowing anymore. You need a truck realistically, but it's an easy way to make $35-50 for 30-60 minutes of work. Helps to have a truck, liability insurance is also good and may be legally required.
Dent repair & car painting If you have a car in need of a paint job or a large dent in it, you'll be approached by a few people a week sometimes offering to fix it for 200-400 +materials; this can be a lucrative business for those that know how to do it. Sometimes you can buy a door for $130 for the same model car and sometimes the dents can be pulled and smooth the last 5% with body mould. If they claim the cans of car spray paint are enough, they're probably a scammer and this is a common problem in this field; but if they bring a high pressure paint sprayer then they may be legit. Someone learning these skills can make a middle class income of $400/day each day they work, though some people bring their whole family to do the job and that's not a lot each if they all get a piece. Learning these skills can be a business one can start in a pinch, with only a few hundred in start up capital could make $50k-100k/yr; one guy that was only half way decent at it had a fairly new Corvette implying at least decent earnings. A similar business to get started or in a pinch, is flipping car parts; you can buy a popular modern car door for $130 and resell it for $400-800. I saw a guy with about 20 sets of headlights at the car yard, I didn't check the price on those; but it's one you'd likely try to make some quick cash early on and move on to more scalable options as soon as possible.
Pressure washing a few hundred dollars can get a pressure washer and this might work in a car trunk, but it's another thing you can keep in a truck (maybe get a truck cap so everything is inside, a diamond steal locked tool box can be good too.) A typical driveway takes 30 min and pays $75, if you can find clients you might do 6-8 a day; but deep clean could be $150+ and larger jobs can be lucrative. Driveway jobs use the customers electric and water, but state so in the ad so they don't claim this and expect you to bring a water truck.
Stump removal This is a tossup, the equipment is $5-10k and they charge $75/stump; upfront it's expensive but you might make $1k/day and it's another job that makes use of a pickup truck. It didn't take the guy long to remove those stumps when I hired him and he made $300.
Painting parking lots this can be lucrative, easy to spot potential clients (anytime you see an office building with a faded parking lot, jot down the number for leasing and the address in case that's just a realtor who won't forward your offer. I'd price this service for a 1 day job at $1000 over the cost of supplies and labor (I knew someone who was hired help getting $200 a day, he had work at least 4 days a week.) So you might get other people to do the job and charge $2000. It increases perceived value of the office complex immensely by making it look better taken care of.
Wedding videography-Get a high end camera for $1000 if you're a skilled camera man and you can charge $1500 per wedding (first one might be $500 on the condition you be allowed to show samples as examples of your work), that's almost $300/hr; because you will also have to spend time editing the video. It's a great side business since lots of weddings happen on weekends.
If you're a skilled golfer with good communication skills, you can teach golf for $60/hr.
Drone surveying and videography-Drones at the prosumer level (ie consumer grade that have professional use) costs $1200-3000+ and a drone pilots license costs a few hundred and permits run $150/yr (you can be active for as little as a few hundred and up to a few thousand outside of the actual drone you purchase) but this is a viable side business for someone who can follow all the FAA regulations. They charge hundreds per hour, definitely worth it if you can get even part time work consistently.
3d property scanning for realtors can be a lucrative side gig. Matterport Pro 2 costs $1k+ used and about $3400 new, Insta360 One X is about $200 used. This skill can command $100-400 for a typical house depending on the region and house size.
Digital Marketing Agency For 15 years I've gone from seeing the occasional person doing this to it being a very popular way to make money, if you work hard at marketing the service and know how to run an ad campaign well; you can make good money at it. The way to start is offer the service at $500/month the first month and $1000/mo after, that's not total that's on top of the actual marketing (ie Facebook ads, Tiktok ads etc) once you get 8 recurring clients, start offering the service for $1000/mo the first month and $5000/mo after. It's very realistic to get 1 client a week really working hard, you'd have a $100k business in 8-12 weeks. Day 1 of each new campaign would be 2-12 hours, then maybe 1-2 hours a day the next week, less than an hour a day towards the end of the first month and probably an hour a week in month 2+. The 2 skills you need to develop are how to market the service (generate qualified leads of businesses with the decision maker email, write an email, talk to them on the phone) and actually running ad campaigns (creating simple ads, putting the ad together on the platform, adjusting based on results.) Once you have a $100k business, you want to turn it into a $1 million a year business; at $5k/mo that's only 17 clients (maybe you look for a month to find each one, in 20 months you've gone from $0 to a million/yr in profit; as there's very little cost in hustling.) Really, getting good clients and retaining them is more important than making money on upsells. If you don't have these skills, or any skills; you could offer 20% to a sales rep and 40% to a marketing expert in each field along with retention bonuses and start a full service agency; getting 5 long term clients paying $5k a month to 5 marketers would be $10k to each marketer monthly and you'd make $25k-50k/month and the sales rep would make $25k a month (a world class sales rep deserves $300k a year, a very good marketer deserves $120k-180k a year and you created all that prosperity and are rewarded with $300k-600k/yr realistically. The challenges of this business are: finding a great sales rep, finding great marketers, client acquisition, top performance for clients, client retention. If you do great work, retention is easy. If you're a great sales rep and great marketer, then you can be a 1 man shop making $100k-1 million a year (with 6 world class employees, you can have a lucrative business on a modest 33% (40% after the $1000/mo trial minus retention bonuses) as actual marketing costs like ads are on top of the marketing fee for running the campaign.
Vending machines- These can be bought used for $600 (maybe less) or new in the 2000-5000 range but if a decent location lets you put it there you can get around $200 a week, and those are at cheaper rates. If you get 10, that's about $100k/yr.
Laundromat- For about $50,000 you can start a laundromat in a strip mall, ideally one not far from apartments that either don't have their own washers/dryers or not enough or not very good; also far enough from other laundromats (though I know 2 laundromats that are practically neighbors, both still do okay.) A laundromat like this can earn $50k a year after expenses, not bad for a couple hours a week removing coins; just set it up to be low risk (might need metal gaurds on dryers to prevent damage, as it's cheaper than hiring an attendant.)
PMB (mailboxes & shipping center): One lucrative and scalable small business idea is opening an independent mailbox and shipping store. You can become an affiliate with carriers like DHL, USPS, UPS, and FedEx, earning a small margin on each package you ship. The main revenue driver, however, is private mailbox rentals. A location with 150 to 275 small boxes at $15/month, 60 to 90 medium boxes at $25/month, and 10 to 15 large boxes at $35/month, at 90% occupancy; can generate $44,000 to $74,000 per year in mailbox revenue alone. Add another $40,000 to $60,000 annually in shipping profits and $36,000 to $120,000 from printing and other services like notary, passport photos, and packaging supplies. Startup costs include leasing a location (around $3,000/month or more), business insurance, commercial grade printing equipment, mailboxes, and a secure interior buildout. In the early phase, expect to work long hours often 60+ hours per week until you cover startup costs and stabilize cash flow. As the business grows, you can hire trusted employees and eventually expand. With 2 to 3 well run locations just far enough apart not to compete, you could earn $180,000 to $360,000 annually in almost passive income, simply by checking in each evening. Some owners even hire managers from day one, depending on trust and capital. Either way, this model offers a reasonable return of $60,000 to $120,000 per location per year for hands on operators, with long term (modest, local) scalability. Lisa Song makes Youtube videos on these, she says she makes $300k/yr (not sure if that's for 2 locations or each) and only spent $60k to start them (both up within 45 days.)
Real Estate Broker If you become a real estate agent, after 2 years of being active you can take the course and take an exam to become a real estate broker. Being a broker equates to leverage, you have office expenses (it can be a high profile storefront or minimalistic office space, as long as it fits legal requirements) and it's no longer the lucrative 50/50 split it once was; but it's still a good business to be in. You may bring them top quality training and incentives, a better split to lure top agents from other firms; etc. You can also be a wholesaler (contacting distressed properties and offering a lowball amount, getting some under contract; selling it for more than the contract price and making the difference as profit) or start a property management service (may have insurance and permits necessary, check before starting.)
Modeling agency Most mid size and large cities have modeling jobs and modeling agents can charge 10-20%, in NYC you might manage 5 models and own an apartment that you rent to all of them (model apartments are often agency owned, making a significant profit off these.) You simply get a talent management license from the state, there's usually a bond (even if it's $50,000 the actual cash amount may only be a few hundred.) Knowing how to market them in your market is the key.
Travel agency or tours To do this, you get a sellers of travel license and a bond similar to the one modeling agencies do. In 2002, I knew a 78 year old man who had known the unsinkable Molly Brown who survived the Titanic sinking; he had sold vacation packages to executives and on top of commissions he got luxury suites like theres on these world class trips. Those packages are unlikely but not impossible due to the internet, but organizing tours (often for senior citizens or people just graduating high school) can be a lucrative market that allows people starting this business to make money and travel if they have a knack for it and know their niche.
Imagine working in mowing and moving businesses and saving enough for 10 vending machines, and then a year later starting 2 laundromats. You could hire someone to collect the money for you (ideally a married middle aged former military, or a trusted relative; these tend to be the most trustworthy people for handling your money-as you know if your relative is trustworthy) and then maybe you still make $150k of that $200k and no longer have to work mowing lawns (maybe outsource it and have 10 guys mowing 3 yards a day each for $120/day and you make $300/day off your share for another $100k+ and maybe have 3 moving trucks doing 6 moves a week each where you make $100 after the workers get their share off each ride that's nearly another 100k. So, if you wanted these 4 businesses (probably a mower and mover isn't a cameraman, but that's also possible) and taking in $350k with no work on your part and creating 23 jobs that may go to college students and people who want a job that doesn't take over their life but makes decent money in a few hours work. Some other ideas include pressure washing ($500 set up), mobile oil change (it's costing $50 in shop these days, might pay that without having to leave the house), car detailing, cleaning short term rentals (like air-BNB, better repeat business), cleaning solar panels (you simply drive a neighborhood and anytime you see solar panels you give them a flyer.) The idea is to find something that covers your expenses in 1-2 hours a day or less, then makes money to pile up; finally has money to put into businesses that can pay for other businesses. Owning a chain of laundromats within a region could be a hefty payday if you went to sell, I know if you buy up a couple dozen funeral homes there are hedge funds that will pay a premium for the portfolio that wouldn't buy a single funeral home.
At this point, you can sit back and enjoy or take it further. You can buy businesses like laundromats, service businesses, franchises (one of the hardest to justify, a McDonalds Franchise can cost millions when you include the money the franchisee pays for construction of a building they don't even own), real estate, stocks. Personally, if I went this route (labor businesses, vending machines, laundromats); I would probably put profits into stocks (probably sp500 low fee index fund) as the rest are just added stress and none of these are things I'm passionate about. An interesting point of view I heard, you don't need to love your business; save the things you love for when you're not working. An example of this is someone who loves to go fishing might not love being a commercial fisherman, a leisure activity becomes work. If you take a salary of $100k and invest the rest within a corporation, you'll have $275k after corporate taxes (your 100k would be taxed separately) and can invest long term and allow those gains to compound and only pay the 21% corporate tax rate (or applicable taxes of the day if they change) on gains "if" you sell until you eventually close out positions and take it as a dividend that has a 15-20% tax rate.