Best bet is to get inspections and or professionals out to assess the systems and provide estimates.With the roof 20-50 years depending on the climate, area, type of shingle and type of roof.

You could make an offer with a due diligence period to give you a chance to get inspections, and check for any environmental issues (cars leaking fuel, oil, etc... could be an issue). 

I would want to add an inspection contingency to the mix. 

If it won't pass FHA or VA inspection it will be tough to get a buyer who has financing.

I am requesting 14 days for inspection and that is the only contingency I have, or I am willing to wave inspections.

If CFK is not successful, our 90 days starts right away instead of losing 2-4 weeks in scenarios where the occupants say they want to do CFK, then go dark because they're really just stalling.Post whatever notice you have to do at the same time that you make contact just in case CFK doesn't work.Remember, they need to sign the CFK agreement first (do your first interior inspection at the same time) and then they get their check on the day of the move-out after you verify the condition of the inside is the same as your first inspection and that it's in broom swept condition.

A/C unit inspections, Roofs being installed over old ones.

I had the house inspected and there are some items that will for sure have to be repaired prior to me renting it. 

I only use A Healthy Home Inspections, Troy Thornhill.

With the tenant living there I wont be able to inspect the house, though the owner already told me what needed to be repaired.