I’d Prefer to pay off Any non 30 yr debts associated with a project before starting another.

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. 

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. 

The tenant wishing to expand was recently acquired by a very large nationwide medical corporation.How do you work out new leases with existing tenants, when you're not yet the property owner?

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. 

How many here are in the medical field in any capacity?