For starters, there are situations where a sealed crawlspace is OK. And there are situation where there are NOT. If you, a friend, or a family member know someone in the HVAC business, see if a 'quick $$$ tip' to have that person come over is possible to do an evaluation. (Maybe someone knows a builder.) This way for a few $$$, you can get some good advice. It's worth it! You're probably making decent $$$ on the home sale so invest a few more $$$ for some good advice. Again, depending on the big picture, you may or may not have to cut openings.
In the meantime, I know that VA inspectors are the toughest ones in the business because they're heavily regulated. If you don't do what he wants (assuming that's what has to happen) the inspection fails and the sale collapses. On the other hand, non-VA and non-FHA inspectors would 'note' this problem to the homeowner/potential-home-buyer and you'll all simply work it out. Before I answer your question, as I said, this needs to be analyzed from a big picture perspective. You can opt to say to him, "See ya." Or, you can opt to see if you can do the patio work and have the home buyer put $$$ in escrow for the vent work. In short, the buyer and prospective home owner split the costs.
Now, w/o knowing the big picture, I've got a WEB page that talks about more than just the proper venting of a crawlspace. It talks about condensation too, and so on. It's Crawlspaces and Condensation. Your question is definitely answered in there! BUT, as part of any good education, you ought to read the whole page. And don't forget to think about spending a small 'tip' to get some good advice. Tell your friend or family member that you'll pay, say, $30 for an hour's time AND perhaps a phone call or 2 later should you have any ???'s.