it is the same contract.
On the line where is says "seller financing" you cross this out you write "via agreement for sale, as per Appendix A".
In Appendix A you list the terms, such as a house for $300,000 with $20,000 down and a $280,000 AfS:
Appendix A - Agreement for Sale Term
AfS for $280,000 payable at 4% annual interest, payable monthly at $1200/month, with the balance due on October 5, 2014. Purchaser to pay all taxes and property associated fees such as utilities, condo fees. This AfS may be registered as a caveat on title.
Other countries, such as Australia call an AfS a "wrap mortgage" which explains the concept better. Essentially you wrap your interest in the property around the existing first mortgage.
Ensure that on October 2014 there is enough money paid to pay out the first mortgage. Say the AfS is now $265,000 you owe the seller $265,000 and with that he pays his first mortgage (also paid down by that time), and at the same time you re-finance, based on a value of say $320,000 you get a new 80% mortgage of $256,000. Thus you are short, in this example, of $9000 to pay the seller off completely.
It is common to line up the AfS with the first mortgage date due to mortgage penalties.
