If mom is going to live there too, it is simple they are both on the lease.

This answer is simple, yet elegant. 

Since you are in NC, historically I would think a simple broker's option contract would work.

Simple post the deal in the local forums and indicate you are looking for a HM lender, 

If the system is supposed to be so simple, why can't a human walk me through it in a couple of hours. 

Then I would only offer a deal that was SIMPLE.

A DIY way of starting your investigation is visit the building department and see if they have any records for the property on file.

Rently has been working for me its pretty simple, the only Issue I had was with stupid people not following directions when putting in the code to open the lockbox, but I was able to walk them through it on the phone.

Which one (usually, and I understand it's not simple) has a better resale and long-term potential?

This is where a simple, old school paper application/word document will serve you well.