Welcome to BP Kevin. I have done several HUDs over the past year and have never done a professional inspection on one of them. I am buying SFHs less than 10 years so I don't have to worry too much about structure, roofs and heating/cooling systems. I use the HUD inspection as a guide but do not rely on it to be 100% accurate. The problems I have run into have been minor so far (I do understand that I will get hit one day for a major expense). We had a cold winter this year and lately have run into several problems due to the houses not being winterized correctly. I have closed 2 in the past couple of months and both water heaters were drained without turning the power off. New heating elements on both. One dishwasher pump was not drained and froze and had to be replaced.
The problem with HUD is that you can have them inspected, however you have to turn on the utilities yourself at your expense and HUD will not fix anything and to my knowledge will not renegotiate. You will loose your EM if you fail to close for any reason. And you have to pay to have it re-winterized.
If I was doing older properties, I would have my contractor walk the property with me to help check things out.