Can I request a credit report on the buyer? Is a summary statement as good as a contract?

Not only can you, you should, and the lower their credit score the higher down payment you should require and the higher the interest rate should be. There is a reason people have bad credit, they don't pay their bills on time. Also you should know exactly how to foreclose if it happens.

And no a summary statement is a summary statement, you should have a contact for sale, you have to include any and all required legal notice, itmes like lead paint, or terminte and so on. And you have to have a loan agreement with is filed as a lien on the home. If you are going to hold your own mortgage get a attorney to do all of the paper work for you.