Further to my emails to Brian, here's a bit of info for other members.
A SENET is a promissory note, voucher or IOU. Although you obtain them from banks, the bank is not acting as guarantor for any money involved.
You get the form from a bank and just fill-in the blank spaces. You can have the form notarised, or not.
If the purchaser backs out of the deal, you can use the Senet to take them through the courts, but even if a judge agrees with you and decides that a custodial sentence is appropriate, the sentence could be served by the accused and they could still retain the property and the outstanding money.
It's unlikely that a Turkish person would accept a Senet in a transaction in the current economic climate.