Many contracts contain a clause that states that it is OK if it is signed in counterparts and a fax copy is as valid as a "wet ink" copy. Ask if he can sign by fax (or by scan) and see what the response is from the other side. I do this routinely with both court orders and contracts; so long as everyone is provided with a copy with all the signature pages attached, it is a valid agreement and enforceable against the party to be charged.
The only reason why anybody's signature would need to be notarized would be if this was a lease for longer than one year. If that is the case then every signer's signature would need to be notarized. He can have a notary witness his signature out of state and add their jurat (that is the notary stamp and the statutory language).
Using Avvo does not form an attorney client relationship.
Usually a counterpart or copy is fine if the contract has a provision allowing counterparts. A notarized version is OK but not necessary for enforcement. More important are the conditions that the co-signer would be responsible as well as a jurisdictional clause so you don't have to sue out of state.
Only If and until you and I sign an Agreement for Legal Services, I am not your attorney. These answers are provided for informational and/or novelty purposes