@Jason Dillard"if you're tired of tenants, toilets, and ... "  (cue banjo music)

What if the tenant becomes non-performing?

Some folks look at commercial buildings as 5+ unit apartment buildings or a warehouse or something like that while some lenders and Dodd Frank legislation look at a simple, single family residential that's non-owner occupied as a commercial dwelling because it generates income. 

Assuming your state codes allow you can simply give notice to non renew any tennat that does not comply.Raise there rents, replacethem, do as you please.All completely dependant on your state codes that you must learn asap. 

We moved in during the sale process of the house, and were verbally promised a few things, washer & dryer, lawn, and one of the two available parking spots.

I have a non-monstrous income of $150K. 

Figure out the eviction if they are non-paying. 

Having the license can also open up some salaried (non commission) type jobs like property management etc. 

But if he has bad feelings/is annoyed/feels put out by his father selling the building, there is a good chance he will take that out on you and be non or late paying and/or a PITA. 

We've done the same with another non-medical business (Jiu Jitsu gym) that I'm a partner in.