You most certainly can put an offer in, if excepted by the sellers than you become the backup offer. Generally what happens is that the first contract is contigent upon the sale of a home, usually they sellers have a 48 hour kick out clause. This means that once your offer is accepted, the buyers with the 1st contract will be contacted to remove the contigency, if the buyers can not remove the contigency, then the seller can release them from the purchase, and accept your contract instead. This will put you in the buying seat, so by all means if you like the property, don't let this contingent contract prevent you from putting an offer in. I hope this helps in your understanding of this type of contract.