Call your accountant and your attorney. Lending money to someone who is buying your home will affect your income tax situation. Interest earned on the loan is taxable income. The loan documents should be drawn up by your attorney. Set a shorter term.
Balloon payments are common too.
Consider the collateral. Your loan to the buyer should be secured by the property, so you'll be able to foreclose and evict the buyer if he or she defaults on the loan. The home should have an appraised value equal to or higher than the purchase price, and the buyer's downpayment should be at least 10 percent of the purchase price. Otherwise, you could end up foreclosing on a home that can't be sold to cover the outstanding encumbrances. A sizable downpayment also reduces the likelihood of the buyer walking away from the mortgage obligations.