Seller Finance or Option- Please help

[Joe Delgado]

Hello.
I want to first thank all of the knowledgeable folks out there who take your valuable time out to help, inspire, share, educate and just bare with us newbies.

Well, here it is:
I am in the New York area and I found a home owner who is willing to sell her house with seller financing. Being that I cannot afford the house at the current market price, I pitched a 10% down payment at closing and affordable monthly payments of 2K till I am able to refinance the remaining balance after 5 years. The seller asked how she can be protected in the event I am not able to get the financing after the five years. I told the seller that we can set up an option but the monthly payment will go towards the agreed upon current offer. Ibeleive a refi is much easier to get than a new mortgage. I asked the seller if 100 percent of the payments can go towards the current accepted offer, she accepted. This may sound too good to be true, but she is motivated to move, and the current mortgage procedures and qualifications are preventing her from selling to the general public.
I believe this a good deal since there is no interest involved for 5 years. Equity is building up within those 5 years so I am offering close to market.
I wanna thank you in advance for your generosity in your wealth of knowledge.
This is the deal I am trying to stucture with this seller. Any advice is extremely appreciated.

SFH: (Two fam zone)
Market value: 620-650K
offering: 600K
Down Payment:60K
Monthly Payment: 2K/5years=120K
Balance:420K (affordable for a refi)

Thanks,
Joe D