In the event a lease could not be presented we asked for same proof of payment to establish rent amount if that was disputed.

There's lots of advice about ways to build credibility.

For example, a builder will construct a retail establishment for an owner, and the builder will receive a percentage of the gross receipts for a specific period of time.

. $395.00Calculators - Discover How Banks Approve or Deny Your Short Sales.PricelessToday's Investment:$797.00The main value I could possibly see which is key to the process ie getting the homeowner to sign over the deed while holding the financing their name is based on access to his website that includes seller testimonials ie he says this will build up your credibility.

If so, how do I establish values since there is no sales price?  

If they already have taken possession, then they are testing you and you need to stand firm on the policies you established when they moved in or they will walk ALL OVER YOU for the remainder of their lease. 

Since I emailed him I have discovered my local Real Estate Association and have made plans to attend their next meeting in hopes of establishing a connection there.

@Reginald Smith JrI LOLed when I saw your post as I was told the same exact thing by a well established real estate attorney recently.On the bright side, I see more and more law firm booths at my local REIA :)

Before screening, establish your minimum criteria to rent.

I presume that came after you established a track record of successful flips.