You can't get out of the contract to build the house--since the whole point of a contract is to bind or obligate the parties despite changing circumstances or changes of heart--unless one or more of the following four things occurs:1) There is some cancellation clause in the contract itself and you comply with its terms.2) The contractor knowingly or intentionally lied about something to get you sign the contract, in which case they committed fraud, which will let you void (invalidate) the contract.3) The contractor breaches or violates a material or important term of the contract, which would let you terminate it.4) The contract becomes physically impossible (e.g. a sinkhole opens up on the building plot, so the house can't be built there) or legally impossible (e.g. the local government will not grant building permits).Otherwise, you are locked into the contract you signed. Your retiree status and disability status have no bearing on the contract's enforceability.