Dealing with bed bugs and other pests has made me apprehensive about purchasing used furniture. It's a shame because you can usually find great deals on FB Marketplace, Craigslist, Kijiji etc.
Though and I say this anecdotally, when I moved back to the States I ended up refurnishing most of my house using street finds. We're talking like 10 different furniture finds include a futon frame (we bought a new mattress). Only 1 of those was upolsteres but was in great condition.
No bed bugs, I got lucky.
Edit/addendum: The bed-bug-sniffing-dog, while a very good boy, is a total scam.