Army Corps of Engineers projects that could mitigate the potential for future storm damage.The list is not all-inclusive, and other projects could be added down the line. 

Let the lease run it's term then decide if you are keeping her or not as a single tenant.Bottom line is she is going to have a difficult time and you would be better off getting a new tenant.

These same portfolio lenders should also all allow you to transfer it but that shouldn't be necessary if you start with an LLC upon purchase.I work for a lender that offers a line of portfolio products along with the other loans mentioned above. 

I had initially planned to finance the rehab with cash and creative financing (lines of credit and such), and then financing it all through a bank.

I must admit, I am struggling a little on this one.We already made an offer on the home and the counter was decent, still keeping us below initial asking price.The offer was with indication that we would be doing an independent home inspection, always a smart idea.At first visit to property, there was concern on the diagonal/zig zagging lines in the walls, the few gaping holes where the stairs meet the home – evidence that the staircases had at one point pulled away/separated from the home.This cracking is by no means just settling, my limited knowledge of home construction was telling me, this here was a structural issue.But wait….. there’s more!

Is it ok for me to use a loan or low-interest credit line of my own to pay the mortgage on the duplex before I get renters in it?

This is in line with their goal to protect the tenant.

I'd like to be 1st in line for 2nd ownership.

Bottom line is air bnb is so completely anti host.

Your best bet is likely a local bank.