Most title insurance companies will cease to offer insurance if a quit claim deed is used for the transfer as the quit claim deed offers no warranties as to clean title.Every county requires a warranty deed to be signed by the Grantor (the Investor) and either witnessed, notarized, or both.

Fill out a Quit Claim form with them, both parties sign and notarize.

If it is true that there is no written agreement (most owner's won't remember everything he's written), then you may create a sufficient defense by simply getting a short written and notarized statement from the current owner stating, ""There is no written lease and no written management agreement.

I'd look for an agreement that was notarized, and I would verify the notary's commission was active and then call the notary to verify that he/she remembers notarizing the agreement and remembers verifying the identity of the signer. 

Get everything in writing, signed and notarized so that her siblings and your siblings can see that this what she actually intended.You could set it up as a purchase & sale for whatever amount you felt you wanted to.

If not, are you pretty confident about those rent numbers?

Would a simple notarized letter stating what is going on be sufficient in court ?

He actually gave us a notarized FINAL UNCONDITIONAL LIEN WAIVER even though we had a dispute on the final amount owed. 

Jared, I don't know about structuring the deal as you asked, but I can advise you regarding the deal needing to be legally signed.The ONLY qualified entity that can legally notarize a Real Estate Purchase Agreement is a Consular official at the US Embassy near the location of the aunt.  

I doubt my calculations are perfect (no one's ever are) but I try to be very conservative with all my assumptions.I really appreciate the feedback How much, in dollars not %, are you putting away per month for CAPEX, repairs, etc...?