No, you may not if you are both on the title or deed. If you are, then either he needs to sign any contracts or he needs to give you a written power of attorney (POA) giving you the power to sign for him. An oral (that is the better term than "verbal") promise to give you house is NOT in any legally binding or enforceable. It does not matter how long he is gone for--people can own property they don't live in or even visit, and him moving or staying out of state in no way   gives up his right to or ownership in interest in the house.If he will not sign any listing agreement or contract (and after that, sign the closing documents) or give you a POA, your only option is to sue him in chancery court (a part or division of county court) for "partition": for a court order that because the two owners of real estate cannot decide what to do with it, that the court should order that the real estate be sold and the proceeds, after paying cost of sale and any mortgage, be  distributed among the owners. That is the only way to sell without his agreement. A partition action can be procedurally complex: if you want to consider this route, you are strongly encourage to consult with and retain an attorney to help you.