Private Money Deposit-simple structure

I’m buying a rehab property with a hard money lender who,in return for great terms, requires 10% deposit. I used them once before, this time I’m getting the 10% from a private lender. I figure I’ll need $27K but am asking the private lenders for $35K. I very quickly have 6 different parties lined up and now I’m looking for suggestions on the simplest way to document it short of a mortgage which is out in this case.

I’m going to offer 15% simple interest and though I’m pretty sure I can be done and sold in 6 months, I’d like the flexibility of 12 months.

Thanks in advance

Can you use a notorized promisory note?

Just a thought, assuming your property is the collateral for the money, won’t the lender want to record the loan to protect their interests?