Can you insure a note on a second mortgage?

[Dee Xixi]

I found a great property with good income but bad cap rate for the location. Current owner over spent to rehab the small multi. The area is a c area but owner rehab for a area.

Listed for sale for over 18 months, over priced. For over year seller and I have been going back and forth. Finally I ask seller to carry a note for 20% of the purchase price. The seller agrees but his partner (the wife), is not on board with the idea. Does anyone have any suggestion how make the second mortgage secure either insure it or something. The partner issues is that they used their saving affraid that I dont keep my promess t and they lose everything.