In today's market, few buyers make contingency-free offers. A contingency is an event, like the buyer's loan approval, that must be satisfied in order for the transaction to close.
The purchase contract should specify a deadline for contingency removal. The time period is negotiable; it's whatever the buyers and sellers agree to. Sellers usually want as short a contingency period as possible so that they can make plans. Buyers, on the other hand, often want as much time as they can get to inspect the property, line up financing or sell another home.