Just be aware of what you are getting yourself into. I did maint. for quite some time and Yes, it can be rewardingand fun, just be prepared for some realities. I'm not trying to rain on your parade or discourage you from having a go of it, just trying to offer some perspective.
1) You will probably not get rich off of this. The old joke goes if you want to make a million bucks in the fish business....start with two. Most of the people I know that do this, do it because they love what they do.
2) Be prepared to spend your time up to your elbows in wet goo. Skimate, pond scum, algae, fish poo...just a short list of the noxious slime you can and will at some point be covered with.
3) Long/Unusual hours. You will eventually encounter that special client that can only accomodate on alternate tuesdays in the hour between lunch and their messese. You will also spend a lot of time driving back and forth.
4) Heavy lifting. Salt buckets, water jugs, boxes of rock...
5) Wear and tear on your vehicle. It's very hard on a vehicle. Long miles with heavy, unstable loads, inevidable spillage of corrosive liquids...
With all of that said. If this is something you are truly pasionate about, then go for it. I would love to go back to doing it, but my current situation will not allow it. I also know a few maint. guys that don't even have a tank of any kind at home anymore because the last thing they want to do after work is feed the $#$%!! fish.
There are some things that will make your life MUCH easer. A large van/panel truck. Build LARGE water storage contatainers into the vehicle, one for RO one for salt. An inverter large enough to power a pump that can overcome significant head pressure, and lots of tubing to move this water around w/o having to lug buckets.