The first step to homeownership should be to get preapproved (not just prequalified) in writing for a mortgage. As a buyer, it defines your price range and could save you needless visits to homes you cannot afford. From the seller's perspective, it takes some of the worry away and makes the potential buyer more attractive thereby increasing the chances of a successful and amicable negotiation.
If a mortgage commitment is not delivered by a specified date or any extended date permitted by the seller the contract may be but not necessarily is deemed null and void. The agreement has to be very specific on this issue. Generally there is an obligation on the part of the buyer to notify the seller and/or broker that they cannot get financing. That is generally done in writing with proof of delivery in the form of certified mail or even fax transmission. In that event, the buyers deposit monies are usually returned unless the failure to obtain the mortgage was the result of something the buyer did or did not do. It must be noted however, that mortgage commitments usually contain contingencies and are not guarantees that the funds will be made available at the time of closing. For example, if you unexpectedly became unemployed the mortgage company would not likely lend you the previously pledged cash and, unless this event was specifically addressed in the agreement, you risk losing your deposit monies.