Offers contingent on a buyers’ ability to sell his current residence are increasing in popularity. They were almost unheard of during the go-go early 2000s, but common 20 years before that.
Sellers generally don’t like these kinds of offers because it puts them in limbo. If their buyers’ home doesn’t sell, they can be back at square one. Also, once sellers accept a contingent sale offer, they must disclose this to other potential buyers and that can discourage a buyer prepared to make a better offer.
Sellers who accept contingent-sale offers can include an escape clause in the contract. This clause allows the sellers to notify the contingent-sale buyers of a competing offer and they must remove the contingency in 72 hours (on average) or lose the home.
Source: Inman News, Dian Hymer (08/16/2010)