Call them and ask some preliminary questions, asking first if they have a moment to chat so they can either be honest and call you back, or stop what they are doing to focus on you.

Once I have the ARV appraisal in hand from the construction loan from the bank, that will help me make the preliminary go/no-go decision on the BRRRR. 

Even better if their under developed for the zoning: I have one client in particular who purchased a 10k sqft lot in late 2017 for $450k with a dinky SFR on it, and did preliminary plans showing 6 units (from a draftsman, not an architect), and flipped it for $750k a year later.

Even then, it is outside the comfort zone of many (perhaps most) people.If you are going to pitch an owner carry, you probably want to have a preliminary discussion before the Owner engages a listing agent.  

While doing your preliminary underwriting; figure out the expenses for running the property and for renovations upon purchase.

I have never heard of a "Preliminary Change of Ownership" form.

There are ways to protect yourself when working on properties if you are a contractor/sub-contractor and that is called a preliminary lien.

Auction.com typically provides a preliminary title report on the properties for buyers to review prior to the auction date.

Just my preliminary thoughts.

Get the contract with whoyou think is on title, the seller should tell you, give a copy to the title company and ask them for a preliminary search, that should be free if they are doing your closings.