Personally I would never accept second hand beds or fabric furniture in trade, off the internet, or at garage sales, etc. The chance of bed bugs is just far too great. There are a few places that sell gently used beds - I would only patronize them if they have a policy about cleaning and treating furniture for the bugs.

Try IEA or furniture stores. It is illegal for them to sell mattresses that they have taken in on return but they do sell at large discount their demos from the showroom.