I would definitely seek the advice of a very competent real estate professional, or an attorney as what is being proposed is a very unique transaction. Here is an article on the Due On Sale Clauses that will almost certainly have been included in the promissory note of your mortgage. If you own the house free and clear, you can disregard the due on sale clause discussion.
It is my opinion that contracts for deed will become more and more common as interest rates rise and otherwise solid buyers are harmed by the economy. Weigh your situation carefully though. You will want a large down payment to make it worth your while and the buyer should have a valid reason for their credit woes.
Consider the laid off engineer who lost their house because he/she couldn't find work but has now secured new employment and has a nice downpayment for you, but skip over the first time homebuyer with minimal down and bad credit because they were irresponsible in the past. Chances are they will be irresponsible again and this time you will be the bank for them.