I'm setting up two LLCs with one for the flips and one for the rental properties.The flips will be an S-Corp exactly as you said to try and make room for some of that income to be taxed at a lower level.Having the separate LLCs is necessary not only for legal protection, but to keep the accounting separate.

@Ryan Canfield to get another FHA loan for increase in family size, you have to provide evidence of increase of legal dependents, and the LTV on your current primary that you are vacating must be 75% or less.

Give him a document that you sign that states if he leaves the property vacant, clean and upon giving you the key's you will return his deposit...

No legal advice given

With all of that being said now my question is, what type of documentation do I need to keep to prove to the banks in the future that I have been managing this property my self??

If it is 15% down they could get a lot of money from you upfront and then get full recourse against you selling at an inflated price.One scenario non-recourse you learn on the property and then hand it back with minimal losses if it turns out to be a real dog.The other situation is they have full recourse against you on the loan, they sell you an inflated price, you put a bunch of money down 15%, and now they won't let you out of the dog of a property and every waking day you are dealing with problems.Owner financing can be great if set up properly.No legal advice given. 

In other words DON'T hire an attorney and keep your day job for entity legal issues and those pesky tenant lawsuits than will come up.One secret of the rich and wealthy is corporate credit or business credit based on an EIN instead of SSN which drives commercial financing deals.

I had a group of nuns that offered to pay a year up front, I told them I can't legally do it, but they can give me 12 post dated checks, which they provided, and I accepted.

Realtors, Contractors, or anyone who has any advice on investor friendly title companies, the correct and legal contracts to use.

My option document specifically says, The buyers will pay all closing costs.