Roofs and attics
Electrical and Heating
Any other hazards or property access problems
If you have some concerns you could get a home inspection done by a licensed home inspector prior to putting your home on the market. He would be able to give you a list of any needed repairs so that you could address them prior to getting it under contract. Also, there are renovation loans available to buyers now as well that would allow them to buy a home that needed some of the required items listed above like the FHA 203K loan product. But to get top dollar it's important to have a move in ready home.