Basically FHA's inspection covers safety, structure and mechanical issues with the house. While some items may seem very minute and picky, they will always fall under one of these categories.
Safety - chipping peeling paint is a risk for someone ingesting lead based paint, no railings on stairs is a fall risk, no smoke detectors, no carbon monoxide detectors, faulty wiring, mold, etc.
Structure - roof and foundation and siding must be sound. Flat roofs require an automatic roof certification from a roofer. Peaked roofs must not have any leaks, etc.
Mechanicals - all major mechanicals must be in place and safely functioning - gas (furnace, stove, etc.), electric (all outlets, light switches, etc.), plumbing (toilets, showers, sinks, etc.).
I remind all of my borrowers that the inspection is there to protect you, not to prohibit you from purchasing. I remember some borrowers who begged me to talk to the inspector to change his mind about what he put in his report about suspecting mold in the crawl space because "they knew that it was not mold, it was just dirt, and we need to close tomorrow". I told them they did not NEED to close tomorrow, even if they need to now live in a hotel for a few days, it is best to get a mold inspection and wait. Anyway, the mold inspection came back toxic and requiring over $200,000 to clean up the house. The house was selling for $75,000. My borrowers were extremely happy that I did not listen to them.
Just because a house is old does not mean that it won't pass. I have financed plenty of older homes with FHA financing. I will say that there probably will be something that needs to be repaired prior to a closing with an older home, but it isn't the end of the world. You or the seller repair what they are asking for and get it reinspected and then close.
If you are in love with a house that doesn't look like it will pass, you can always do a 203(k) rehab loan. Ask your lender about that option.
Let me know if you have any questions!
Mortgage loan officer for the past 10 years, real estate paralegal for 10 years prior