home inspector--can I sue?

my son just bought a house in upstate ny and he has an inspectors
report that says that the heating system may need to be serviced and a
zone valve replaced. It turns out that the plumber came in today and
said that the 3 wire milli volt system which was in the house about 10
yrs is completely worthless. He said the system is no longer made. A
new system will cost $4000. To replace the zone valves and rewire the
system will cost $800. There were other problems with the heating
system which were not mentioned which would have caused the furnace to
flood the utility room.
My son dealt with some scumbag outfit that does "everything", finds
the house, gets the mortgage financing, does the closing etc. I told
him to forget these people but he went ahead anyway. The reason i am
writing this is to see if anyone else has had similar experiences and
whether or not they were able to sue these slimbuckets successfully.
Are there any legal precedents for what the inspector has to put in
his report and what he should be able to tell you? For example, the
heating system is going to cost $ x amount of dollars to fix. We have
to sue because winter is here and my son is in debt up to the hilt
just to get the house.
thank you.  p.s. he told me he hired his own inspector.