Attempting to buy my Grandparents home

[Bryan Tomko]

Hi everyone. Long time lurker here. 1st time investor .My situation is the following. I am trying to purchase my Grandparent's home. 3 bedroom/1.5 bath 1/4 acre lot, 1 car garage, driveway . built 1955 Easton, Pa (West Easton, fairly nice area)

Grandfather passed away in February, since then my grandmother has been in a home. The home needs clean up and some cosmetics but the house is solid. 

My Father and his siblings have had offers from a flipper 1st time 75K then came back with 90k with 5k down and the balance at sale of property after flip. 

Realtor said they could sell for 130k with some small fixes.

I took a friend who is a realtor/investor in the area who rents 5 other homes within 3 blocks through the house and he thinks i could rent for 1200/1300 per month 

I've offered them 100K seller financed 4.5 % interest Amortized over 30 yrs with a 1 yr balloon (plan on taking out a bank loan to payoff. Using calculator i am estimating cash flow to be at around 450.00/mo and after bank loan to be around 250.00/mo

What can i do to convince them to accept this offer?

If my grandmother passes within that year what happens to the seller financing?( I assume I would pay the estate?)

I have an appt with a local real estate attorney monday. Just looking for imput