“My question is can a co-signer for real property restrict the sale of the property if both names are on the propery mortage contract.”
Typically no. Further, if you have to end up making good on the debt because the primary loan-holder defaults, your only recourse will be to sue the primary loan-holder, while the bank can still end up with the property! Generally speaking, if you want to be able to exercise control over what happens to the property, you need to take title to the property jointly with the other party. Of course, this is all subject to the laws of your state, which may have non-standard rules regarding the rights of co-signors.