That can be used to buy down the mortgage rate or reduce closing costs. 

You might find a HML hard money lender that may offer this but your going to pay a ridiculous rate and points/fee's.  

Quote from @Pete Tarin: How does one go about assuming someone's mortgage with a better interest rate when purchasing a property? 

It's challenging especially locally these days with today's interest rates.

Although you plan on having your mother live in the home to start you'll want to assess the home using the current rental rates and values in the area.

We also get to enjoy our place as often as we like (the slightly lower occupancy rate due to our use is also a factor in being cash flow negative) and the negative cash flow is offset easily by the equity we'd gain, even assuming only a 2% appreciation on the cabin. 

I would look for a bunch of Sub To Deals with 2-3% interest rates ...... then rent out for cash flow and huge equity build up when rates are really low (check out amortization schedules and compare 2-3% vs 6-7% with the same balance and length of time - check out the principal portion each month - the lower the rate the higher amount goes to principal PLUS better cash flow).

Aside from restrictions, the thing that is surprising me is the low cap rates. 

congrats, what kind of rate did you get on the seller finance?

Hi fellow investors,I have several owner-financed mortgages in my portfolio with interest rates of 10% and higher.