In most states, I believe the buyer has significantly fewer rights if he defaults (e.g., misses a payment or two because of a medical emergency) if he is using owner financing than if he finances through a traditional lender and actually buys the property up-front, subject to repaying the lender. The laws on this also vary considerably from state to state.
I have no idea how much you're planning on paying, but assuming it's over $20k I think you'd be nuts not to hire a lawyer to explain the consequences of using seller financing vs. traditional financing, and to make sure everything else is in order. Ask around, get a recommendation.
I know of one real estate guy who has done quite well selling and financing homes to buyers on 10-year contracts, and somewhere along the line the buyers have missed some payments and he's taken the properties back, with the improvements made by the buyers and the benefits of appreciation, and the buyers are left out in the cold.
When you buy from an owner who also finances the purchase, the owner (seller) typically has a lot more rights in the property--which is a bad thing from the buyer's perspective--than a bank or mortgage company would have with traditional financing. That doesn't necessarily mean it's a bad thing, but you really need to understand what you're getting into before you sign anything.
In my opinion.