The inspection options are more extensive than they were when we bought previous houses. We found the person who did the last inspection and they will do it again. They work for one of the nationwide franchises. There is a standard whole house inspection covering roof, exterior walls, foundation, grading near the house, interior structure, electric, plumbing, hvac, and major appliances.
Then a bunch of add-ons are available. I'm considering the WDO/WDI (wood destroying organisms and insects), mold in air, mold on surfaces, and air quality (because the house has hot water heat - if previous owners tried to seal up air leaks there may not be enough ventilation).
I don't have prices from this company but I called their competitors early in this process to get an idea of costs. The add ons typically cost $100 to $300 each on top of the cost of the general inspection. Maybe do the first three and do air quality with the radon if we get the house?
Like radon, air quality is probably not a nightmare to mitigate if it is about adding ventilation or filtration (as opposed to a problem like mold). I think; I'm not sure.
It is mold I'm most worried about. And wood destroying things second most worried about. Those can be devastatingly expensive and not easy to see.
They offer fentanyl testing. Evidently, that has become surprisingly common, is extremely hard to remove, and it takes very little use of it to contaminate a house enough to cause problems.
There are other add on options but costs add up so quickly.