As I understand it banks tend to look for 6 months of seasoning prior to refinancing.

From what I've read, banks want to see at least one year of steady rent payments.  

Do I just walk into my local bank and ask them what i'd qualify for as an unsecured line of credit?

in this scenario, the prior owner or bank would have risk of loss, and (assuming the bank carried an insurance policy) would be entitled to the insurance proceeds? 

But I know that the banks don't like me buying another primary residence and buying "down in square footage" Do you have any strategies on how I can go around this obstacle and still be able to buy the duplex, 3-plex or 4-plex with a FHA loan and live in one of the units?

I want to get several quotes from banks/lending institutions, but she wants to interview no less than 15 banks and 5 credit unions and go back and forth with each one and pit them against each other in a "rate/closing cost war" to get the absolute best price. 

The only thing I would take out is having people list their bank account number, I don't think you will have an applicant willing to give that info to you anyway.One other thing to consider, are you charging an application fee?

You wouldn't want to put it in anything too volatile. https://www.nerdwallet.com/blog/banking/best-high-...

It wasn't any one or two of those "typical targets" she mentioned that are/were to blame...it was the combination of all of them failing at the same time.  

It's very unlikely that it'd be illegal if you want to be 100% you'd have to ask the bank or post up the terms of the new loan.