Well.....
I owned a motorcycle custom shop. But I made more money fixing PWC that the local dealers didn't want to touch. I like working on PWC... but sometimes the owners are a pain in the butt. They want things fixed cheap, and fast. They would also get mad if I got into a job, and found real problems. Also... the vast majority of people don't do any maintenance, and the engine bay will be crusty, rusty oily, and moldy. When I got really bad ones in... I would tell them I was going to charge them to clean it first, and they would get upset. (but I told them how to clean it, and said they could do it and bring it back)
I was one of the few 100% honest shops. I wouldn't change anything if things were very bad, and was more $$$$ than they wanted to spend. (Like if I found a melted piston) And, I would give free advice for customers who wanted to try to fix it themselves. Heck... I would let members here, come to my shop... and I would do things like let them use my alignmet tools for free.
Basically... like any job... eventually you will burn out if you are trying to do it all yourself. AND... you may find yourself not even using your PWC because the last thing you want to do, after working on them all day, is working on your own.
If you have the cash to open a big service shop, with other people to physically turn the wrench... it may be different. But being the boss isn't easy either.