If the value based on both approaches is significantly different, the cost basis is not used at all. 

@Aaron S.Seriously, I would make and have made suboptimal financial decisions for happiness; everybody has a different philosophy that's mine.  

But recently they were sold at a very different prices per square foot.

You want to ensure that your lender is doing their upfront due diligence on the deal, has programs to get the deal done if the final numbers come in different(low DSCR requirements, favorable rent guidelines, etc), and is offering you excellent customer service.

I have been buying rentals for a few years and I was looking for an investment that I could have the opportunity to have different streams of income for.

I would use this on the EIN and estate bank account when opened.I was administrator for another estate a few years ago, but it was a different jurisdiction with different rules.

I am finding conflicting information about whether or not this is allowed in Jacksonville, Florida.I've found info stating that the owner must live in one unit and rent the other, or must rent both units to the same tenant, and the two units cannot be rented separately to two different tenants.

As an example in a different real estate “product”, we owned a 70 unit motel that we had converted to mostly low income housing.  

Currently looking at 2-3 $50-60k sfr properties all being sold by different sellers. 

@Noel Dixon The most overlooked thing I see when people talk about assumable mortgages is that, if you can get approved by the lender holding the mortgage, you will need to bring the difference between the loan and purchase price in cash.