Since you're a 1st time home buyer, have you checked into the first time home buyer down payment assistance programs that TN and AL offer?

As far as information, BP has some of the best resources on the web- think of them as your mentor. 

The way you construct the building, how high it is elevated, what is in the lower levels, does it have flood mitigations like breakaway panels, etc. all will impact the eventual rate for the Flood Insurance in the National Flood Insurance Program (NFIP).  

There are programs up to 80%, 30 year fixed loans for ITIN and NPRA borrowers, but you're going to run higher rates. 

All units have been rented to low-income tenants receiving assistance through voucher programs, and I plan to stick with low-income tenants to help alleviate the low-income housing stock in Phoenix.

I'm familiarizing myself with SONYMA (state of NY mortgage agency) programs and I know they require that no other properties be owned simultaneously if you plan to utilize a SONYMA loan.

Not sure if that specific program still exists but it came about due to Covid-19.

They may have programs that use the income from the properties to qualify. 

That is the most common program I know of for 1-4 unit low money down. 

I ran across this cool program by Sears (Sears Home Warrantly) where they will cover up to 21 items at a monthly rate of $70 bucks and a deductible when you file a claim.