Most Real Estate contracts of sale include an inspection contingency clause. This means that the seller, by signing the contract of sale, has agreed to the inspection. I have had a couple of sellers (or builders) show up at the inspection and tell me that I can’t do an inspection (usually, because they say that it is an “as is” sale).
I, calmly, explain to them that the contract of sale, which they signed, has an inspection contingency and that they only way that they can prohibit an inspection is to tear up the contract and pay the buyer a penalty fee (or, at least, give back the earnest money).
I tell them to contact their lawyer (and/or agent) and advise the buyer likewise.
Many new construction contracts, in this area, where the agent works for the developer and is, more often than not, serving as duel agency, specifically prohibit an inspection. If the buyer signs one of those, they are screwed.
Just another reason to have your own RE lawyer and read (and have your lawyer read!) everything before you sign.
Hope this helps;