The big problems to avoid are vacancy, tenants that destroy your property, and tenants that don't pay their rent.  

You have a tenant that has violated your lease, are destroying your property, and you want them to move into a brand new unit. 

- As a result of the seller not being able to rezone it as 3 unit MFH, did the seller (or you) have to take explicit measures to lock the 3rd unit out, by destroying strategic parts of the unit, or blocking any gas/water access to the unit?

We have a temporary shortage of housing due to the floods last year, when around 120 homes were destroyed in our county.  

Just be sure to vet the renters well, dont rush into just putting anybody into the house for you run the risk of getting crap tenets who may destroy the house after you just rehabbed it. 

depending on your areafind low growing drought tolerant plants and flowersyou want something that takes little upkeepany nursery in your area can help you outwhat ever you do, do not plant trees within 10 feet of your residence and if you plant trees make sure you know where the septic or drain lines are and stay away from those areas as well as the water mainsroots destroy drain and water linesenjoy

Is there a way to make it level without destroying my beautiful hardwood floors?

I have an icemaker at my house, but it's my house and if it leaks it has a path right into the unfinished mechanical room without destroying my wood floors in the LR (kitchen is ceramic). 

The last year has been very hard and destroyed my credit.

With bad credit decisions it has destroyed my financial situation.