Good luck getting a PPP under 21. Some counties will issue them, some won't. There isn't any law that says you can't carry if you don't have ownership of the gun. My grandfather has let me borrow some of his guns in the past. If I were to ever be questioned, I would have stated they were his and he gave me permission to use them.
I would just OC and if questioned, tell that the gun belongs to your husband and he is letting you carry it. Being in possession of a gun does not necessarily mean that you are the owner. In reality, there really isn't a way for them to prove who the owner is unless the gun is reported stolen. Enjoy OCing!