Is this seller finance structure possible?

[Armando Montrond]

I am trying to work a seller finance deal, they are only willing to do a seller finance deal if someone puts 50% down. I am not sure if this is even possible or not but the property is 525K. So i was thinking I Could have a P&S drawn up for 262500 (50% of value) go to a bank and finance that part then have them do a second position or just a note for the other half? I hope this makes sense what I am asking, since on the P&S were saying its only 262.5 but im buying it for 525

TLDR; Can I have a purchase contract for half a homes value but really buying the full price with the seller taking a second position on the other half that isnt on the P&S