Treat them like ruffians.2.

If you were the tenant, how would you want to be treated in this situation with the water heater not working?

I like a mix of both world here and both have treated us well, and I’m confident we’ll see the same for a while.

And 20k is more than it would cost for multiple houses unless the termites were never treated, which is rare.3.

I have seen them treated the same as a duplex even when not zoned for such, but it was in an area close to where such zoning was present (so appraiser apparently did not check the zoning). 

You must always think, what if you're the tenant searching for new resident...would you want to be treated this way???

At YOUR COMPANY NAME HERE, we strive to:Return all correspondence within 48 business hours with a plan as needed.Complete all maintenance issues and repairs efficiently, quickly, and courteouslyConsistently improve the aesthetic look of any property we manageMaintain affordability in rental rates and treat our residents with respectProvide exceptional service and support to residentsWhat Is a Lease?

If I do not like the way they do business, treat people, etc. then I tell them to get lost.

Good residents at good properties at market rent don't leave if they are treated well and the place is kept up. 

Use this as a learning experience, make sure your lease covers everything, and be sure to treat everyone the same.