@chohnnyboy My wife use to work as a dog groomer and she had these really expensive and delicate scissors. There was a guy that would go around from groomer to groomer charging to sharpen the scissors.
I would add residential/commercial cleaning to this list. I started a residential cleaning business in July. Slow but steady growth, a lot of money in cleaning. Some companies are making 5 figures per month. Low barrier to entry.
@chohnnyboy I had a knife sharpening business in the summer of 2021. It worked okay, but here's a few mistakes I made:
Targeted people who didn't want (or know) about knife sharpening. They didn't have a problem, so when I asked them, they instantly told me "It's good enough, thanks." better to target people who already need it, maybe the local restaurant?
Didn't demonstrate my abilities off the bat. Demonstration is the best form of proof, so I'd bring a tomato, a carrot, or a piece of paper, and show them how sharp you can make their knives.
Charging very little. I also charged $10 per knife, but considering how some of the knives I sharpened were like $300, didn't seem fair to me. But on a real note. Trying to start a business with cheaper products makes advertising in the future way harder. Assuming you have some success, and then turn to advertising, the advertising costs are pretty much the same whether you're selling a $10 re-sharpen, or a $2,000 landscaping job. I don't know anything about tankless water heaters, but if you can charge that much, it's probably a more sustainable business model.
Also I targeted people from my area (which is middle class.) Should have drove to the "affluent" areas because they can pay more. Plus you can experiment with the ego part "Have the sharpest knives in your neighbourhood." As weird as it is, people, especially rich people, love one-upping their neighbours (I've got the best lawn in the suburb.)
