Contact a local property manager.

So, a couple of years down the road, your seller gets tired of being on the loan and contacts the bank to get off of the loan. 

I also contact the listing agent for the showing and to put in the offer.

Hopefully, based on actual field measurements, past project data, and estimating software, your contractor can develop a detailed estimate that lays out the cost of labor and all materials for each phase of the project.

Shoot me a dm and I'll send you their contact info.

What other data should I be watching?

I'm one of the landlords that mostly uses the credit/criminal checks as a data point to see if they were honest with me prior more than anything.

It was Civic Financial - I’m not sure they do referral bonuses or anything but I can share a contact info if you needed someone.

Personally, I’d review MLS data, Zillow, and consult with a realtor to determine an accurate ARV.

When I tried to contact the repair company to get more details, they informed me that they could not share any information.When I asked the seller further questions to clarify the discrepancy and requested more information, he became upset and stated that he would not provide anything beyond the one-line receipt, which only lists the cost of the repair without any additional details.