Similar to you I was doing well in real estate, had 3 cashflowing properties as well as my primary home and then thought it would be a good idea to flip some early 1900's homes.

Great idea, but check your local regulations.

We sign a contract between me and Don where he promises to make monthly payments to Chase, instead of me making these payments, The idea is similar to assumption, except that the bank does not know, and if Don does not make his payments as promised, I'm in trouble with Chase.

Any other ideas for how to solve this problem?

I have no idea what to expect at this point. 

If you wanted to do a 1031 exchange down the road to use that equity and trade up then that'd be a good idea.

They love the idea of wealth, financial freedom, but don't want to put their own financials on the line.

No way to say for sure since each lender is different and I have no idea of the terms you need or your FICO, but it is typically the prime rate plus a couple of points.

They offer a $10K repair fund to fix damages in addition to SD plus warranty for appliance repair etc.I have no say in whom they choose to move in, whether there are animals, limit on # of occupants etc. they reserve right to inspect property so i have no idea if they can tell me to remodel, paint etc.does this make sense i have a vacancy coming up in October (bad rental timing).

Do have an idea of your preferred acquisition price and how much rehab might be required?