You should plan on 20% down, closing costs, legal etc. and probably another 10K in reserve funds.You should probably spend more time studying finances, real estate and your local area to get a more complete education on investing.

The property was legally converted from a SFR to a duplex at some point in time.

Go to your local community bank - they may lend based on fair market value with no value seasoning restrictions.

Any time a landlord accepts rent payments in exchange for a person to live somewhere, they have created a legally binding lease.

You need an attorney's legal expertise here. 

I believe in MO there is 1 yr redemption period but there are 4 yrs that an interested party can challenge the legal process, meaning that they can not challenge the title itself but they can challenge the County for the foreclosing procedure (example, missing a proper notice etc.)

Proposition 13 and its restrictions.

The large banks will often have their own overlays which are more restrictive than the pure fha regulations.  

Because we knew what legal forms our court used, and I had already downloaded them on our computer, we were able to quickly serve the 3 day notices. 

I have not moved forward with any legal action at this point.