2 - If they deed it back to the original owner, would you guys reverse calling the loan due?

The studies being released show how different industries appear to be increasing their profits with hidden or bogus fees that can harm consumers and companies that have honest business practices. 

Secondly, is it common to do a normal application fee for background and credit?

Well, first, their is a base annual fee.

I'm a licensed general contractor and we prepare bids for a fee if it's a service you need. 

It is not an original idea and I've seen people doing already this in other markets.

Yes, that is the original house hacking strategy, but it really only works well if you've built up enough equity over the time you lived in the first one to depart and end up no money in when you refi.

Rent out your original home.

Insurance has gone up quite a bit, property taxes and HOA fees as well.

Like most others, I am using HML to fund projects: they charge more interest than PM, they charge lender fees and origination points.