@Daniel Galvan I wouldn't say you are wrong...as every investor has a different level of risk tolerance.  

You need to figure out your goals and your risk tolerance... 

The routers we use are capable of both layer 2 & 3 segregation and we provide each unit with its own isolated network segment.802.11 (WiFi) becomes problematic as the size of the building grows:  if you have 6-tenants, each with their own personal WiFi network the interference is tolerable, but once you scale to a 20+ units the tenants access points will be fighting with each other and there will be a lot of RF noise.

You might be able to negotiate a deal even if it is company policy to split the listings on your own property.  

If so and you can get one that has one of those introductory interest rates of zero for say 18 months or so, get that card, transfer your balances to that card. 

My policy for rental screening is "no smokers allowed", however I understand that these tenants pay on time and are nice, quiet people.Because I suppose the damage is already done, should I just let them stay and go through the necessary rehab when they vacate eventually?

This is a huge red flag, if you do not see it you will after they move in and this problem can become something big, all because you saw the sign and chose to ignore what it was telling you.If I were you, I would create a policy and procedure manual and write down like you are talking to someone that is going to take over your position.

However a zero tax Roth is better than depreciation in my view.

As soon as you close get an insurance policy to protect you in case of a loss.  

I bought a probate in Long Island for $385k with zero down that needed way more work than I should have taken on with my partner, as a first flip.