Seller Financing - promissory note

[Nikki Perry]

Good morning,

I am new to seller financing.  I have a house in Fort Worth, TX that I am selling.  I received an offer from a investor.  I had the house on the market through the company I had managing the investment property for $379k.  I have a loan balance for $126k.  Here's the buyer's offer:

Buyer - buy the house for $400k

Buyer - had down payment for $140k (35%) - this will pay off my mortgage, closing costs and seller realtor commission

Seller - receive $5000 at closing

Seller Finance Terms: - $260,000 – Monthly payments of $930.76 per month with a 5-year
balloon Due on November 6th , 2028.
Buyer paying off mortgage in order to seller finance $260,000 with seller

Buyer gets the title at closing

As the seller, I don't see a promissory note for the financed amount and I don't feel comfortable.  The buyer could default and in the contract it just says that down payment is what I get as the seller.  So that means the buyer has the title, possibly not paid the $260k that they are supposed to finance and I lose the house and $260k equity I had in the house.  

How can I protect myself as the seller?  I have other rental investment properties, but this is the first time I am dealing with a seller financed option.

Any advice is helpful!  Thanks!