Buyer wanting creative financing then buyout

[Garrett Finnell]

I'm currently selling 36+ new construction SFR properties at a discount.
I have an offer from a buyer who is asking for a 20% discount (which is more than I'm willing to let go of) and seller financing. 
I want some liquidity, so holding the notes long term doesn't make sense. 

Once we have an agreed upon price, he's going to take some sample notes and get quotes on them from some note buyers (he's a licensed loan originator). 
However, we won't have more concrete terms for the seller financing until we get quotes back from the loan purchasers. 

This whole concept is totally new to me. 
I guess my question here is what can I expect for terms from the buyer quotes, what are some ways I can continue to negotiate this deal, and is this even a good idea to pursue this method of "cashing out"?

We're willing to do a discount and get creative with the financing, but this concept is new territory for me.