If the buyer has actually breached the contract in some , such as by not depositing money by a date that the contract specified he or she would, or by not filling out documentation which he or she was required to upon signing, then such material breach should support your termination of the contract.It's more complex if the buyer has not actually breached yet--that is, if he or she has not failed to do anything required to be done by this time. While there is "covenant of good faith and fair dealing," which requires good faith between contracting parties, that does not require active cooperation. If the buyer has not yet breached, then you would need at least anticipatory repudiation or breach--some clear expression or indication that the buyer does not intend to perform the contract (which again, goes beyond merely being unresponsive) in order to have grounds to terminate.The above is a very fact- or situation-specific inquiry; if unsure, you should consult with an attorney who can review the situation with you.