As a former antiques dealer, I have to agree with the wood/metal/glass furniture is okay, not the upholstered.
When buying for resale, I never even considered upholstered furniture or mattresses. Why? Bedbugs, fleas, human lice, mold, and scorpions.
There is a small danger of woodworm infestation in old wood furniture~
Woodworm is a type of wood-boring insect which lays eggs in small cracks on the timber's surface. After their eggs hatch, the larvae will then enter the wood, eating their way through the timber for anything between 3 and 5 years and then emerging to mate.
There are various tell tale signs that can help you identify woodworm and a potential woodworm infestation. They include:
Tell tale sign 1 - Look out for small round exit holes. The holes will be similar in sizes to the holes in a dart board (approx 2mm)
Sign 2 - Fine, powdery dust
Sign 3 - As the woodworm infestation progresses, gradually you may begin to notice crumbly edges to floor boards and joists. This is simply due to the edges of the timber crumbing as a result of wear and tear around the multiple woodworm boreholes close to the edge of the timber.
Sign 4 - small tunnels that have been bored into the wood.
Sign 5 - If you come across weak or damaged flooring or timber, take this as a signal that something is untoward regarding the timber.
Sign 6 - beetles emerging from timbers and on closer inspection you see more holes within the timber then take this a a clear tell tale sign there is an issue.
Sign 7 - If you suspect a woodworm issue and notice dead beetles close to the proximity of holes in your timber then your suspicions are most likely right.
If you examine the surface and don't see any tiny holes or tunnels, it's probably safe. You can clearly see the damage in plain sight.
When I was a young dealer, I once bought 3 oak shelf units out of a historic hardware store that was closing. We took them apart to move them and found woodworm. We treated it with syringes filled with gasoline. Put the needle in each hole and fill with gas. Let dry thoroughly and refinish the piece of furniture. If an active infestation is left untreated, the bugs can spread to other wood furniture.