I don't expect to make a lot of money but is net 6 figures unreasonable? 

If you feel like you are giving too much away, the deal may be too thin.  25+% total deal IRR is a target hurdle that some sponsors use.

It is not unreasonable for a lender to request from you T1 generals, T4's, rental schedules from T1 and NOA's including evidence tax position is current. 

Here is how it looks like on my phone:There are so many things you can solve by doing automation, although there is a education hurdle to get over.

Should be able to resolve that small hurdle pretty quickly.

Self directed IRA has some additional hurdles but another possibility.It would be hard to imagine a situation where its worth paying the penalty but its possible if the deal is good enough.   

It's unlikely you'd be able to get over that hurdle easily so you'd have to either buy all cash or work something out directly with your dad's ex.

All of this to say, I’m curious of others experiences selling by owner, and potential hurdles/pitfalls I should be aware of.

I hope first few payments are the only hurdle....

That is a request that is unreasonable in my opinion.