If she backs out before the predetermined date do I make her responsible for rent fee, or just keep her security deposit?

Showing him the numbers of course is the best way to secure this deal.

I believe this takes 3-5 days unless the sender opts for Instant Transfer and pays a fee.I think Zelle is the least expensive, fastest and most secure method of all these online methods.

Per Fannie:If the mortgage loan being delivered to Fannie Mae is secured by the borrower’s principal residence, there are no limitations on the number of other properties that the borrower will have financed.

NOTE:  Their security deposit still needs to be the non-discounted rent total!

I've calculated my number - how many units I want to get to where I feel financially secure and content with my real estate career.  

It turns out her old landlady in a similar situation had brought out a contractor and made a lot of noise about replacing the whole vinyl window, and finally charged her $70.00 for an entire new screen frame shipped from the window manufacturer.Same landlady who ate my tenant's security deposit and had never heard of giving notice before banging on the door.

I would like to secure my friend's loan with a lien on the property in 2nd position.

There's another one by a securities attorney, Gene Trowbridge, "it's a whole new business".

Also, review the closing documents to ensure that the tenants' security deposit is credited to you and that it matches what is in the lease agreement.