But what jumped out to me was the immeasurable in terms of dollars:“But our family has grown!”

You are doing all the right things right now in terms of gathering great information.

Yes typically, but generally should be possible to do one with no prepay or very light (say 1% if you prepay in the first year). 

Find a lender who understands your long term real estate goals and understands that rental income can help knock down your DTI to qualify for more loans and acquire more properties. 

AFRs change monthly and can be found here:https://apps.irs.gov/app/picklist/list/federalRates.htmlYou need Table 1 from the monthly Revenue Ruling.Currently, the rates are around 1% or below, depending on the term and size of the loan.

It sounded like another term for assumable mortgage, but I appreciate the clarification.

I rented both, furnished them, and listed them on mid-term rental sites like Furnished Finder.

I'm in miami dade county as a focus area only if you consider ground up but I'd pass on auctions because they are sight unseen most the time and it's all cash purchases typically. you have no control. in land development and real estate development you have full control of every part of the process. don't buy something 50 years old or 100 years old. 

We’ve been searching for a couple of months now, but we are facing challenges.It seems that everything on the market is being snapped up within less than a week by more experienced investors who can offer better terms.

Does anyone have a long term relationship with them who'd care to comment?