Can a seller finance a portion of a down payment?

[Jonathan Norris]

I am looking to purchase an investment property in Los Angeles.  I am working with a hard money loan company.  Unfortunately, I do not have the entire amount of the down payment.  My neighbor would like to sell her house to me.  The problem is I need $60,000 to cover the rest of my down payment.  When working with a hard money lender, who will I hand the check to when the down payment is required?  Can the seller agree to finance the other portion of the down payment?  Last, can I add that agreement in the purchase contract or does that have to be a separate promissory note?