Here there are numerous Generac and Kohler licensed electricians who can do the HO's generator maintenance and repair.
The only thing with Generac is that if you have the liquid cooled models, that requires a separate (and more $$$) contract for the EC with Generac, so few ECs here have the ability to do the liquid cooled models. A 22kW should still be an air-cooled unit.
I've done maintenance on them and they are pretty easy to work on. The parts you need to carry on the truck are a pair of plugs (2-3 types), a few oil filters, air filters, oil, an oil pump/waste drum setup (a small 12VDC pump with alligator clips that work off the generator battery, atop a 5g bucket inside a milk crate works great), spark plug wrench, gapping tool, and a battery (can purchase day of scheduled maintenance to avoid taking up room in truck), factory service manuals that include all fixed models 7-24kW, and an allen wrench of the correct size to take off the side panels. Spare keys and fuses are good too.
All that ^ will let you work on virtually all air cooled Generac generators and do the PMs on them.
A lot of people dont want to do small engine work/repair, however the profit margin on them is pretty good*, especially if you have a helper knock out 20-40 semi-annual PMs over the course of a few days/week. You can schedule the PM work around other work or slow times.
The flip side is that you dont want angry phone calls during hurricanes from customers with a generator and no power. MY ex boss kept a list of his generator customers and made sure they were "green light" if a storm was expected. We did not get a single call for a generator problem once the storm hit.
You might want to do a complete install, to include service work. Personally, I would not buy a home generator from an EC that doesnt also service them.
*Once, the boss dropped a bolt down in the engine cover and it got wedged between the block and the flywheel. Took him and a helper (Me) the better part of 16 hours to take the whole damned thing apart to remove the flywheel and put it all back together. 4 of those hours were drive time to locate a flywheel puller that would work. That one incident made him never want to work on generators again.
Also, Generac had a recall on the throttle bodies on some models, I believe the 16-22kW Guardian units. It was warranty work, but what Generac paid us to do it wasnt very good iirc.