I would be surprised if the lender will actually approve and go through with the short sale, without the mortgagor's cooperation, in spite of your POA.

From Ned Carey's description, you might want to search for "cooperative lease option", as they seem similar in description.

Do you know of a way to get my Ex to cooperate? 

The bank will not cooperate with me to refinance, the home is in a less than stellar place so rent is not a great option, and my mom owed more than it is worth.

If Wells Fargo doesnt cooperate you (or the seller most likely) could go right to HUD.

Enabling uniform cooperation among all state agencies with supervisory or examination authority will greatly increase the effectiveness of the CFPB.The greatest initial impact from the MOU, however, likely will be in the area of enforcement.

The affidavit must be executed, dated, and acknowledged after the date of the written offer of lifetime lease.Suggested documentation includes:A copy of the lease agreement showing the tenant's name and address of new residenceA copy of the purchase and sale agreement showing the tenant's name and address of new residence.A copy of the most recent utility bill showing the tenant's name and address of new residence.A copy of the voluntary move out agreement showing the tenant's name together with a copy of any consideration paid.Or, other compelling evidence supporting the contention that the tenant has voluntarily vacated and terminated their tenancy.Unfortunately for me, my tenant wasn't very cooperative and wouldn't give me a tenant affidavit and insisted that her email documenting her intent to move-out should be sufficient. 

you fix the place up and rerent ASAP to mitigate damages. any damages are paid from security deposit and a statement as such is mailed out in compliance with your local regulations. then, if your new tenant does not come in until april, you bill old tenant for any days unit was vacant. assuming they paid march rent on time, if you rerent in march, you have to refund any days not vacant. you cannot collect double rent. in the meantime, tell tenant now that you understand his problems and want to do everything possible to keep it from negatively effecting him, however, he has signed a legally binding lease, and if he does not pay april rent, you will file for eviction, which will stay on his record for 7 years. his best option is to help you get a new tenant in there before april 1...no harm no foul. his next steps need to be cooperating with you so you can get handymen in there to assess damage and plan for turnover. tenant can also make sure everything is as clean as possible, as soon as possible. in no way shape or form should you let tenant repaint or even consider repairing anything. that should only be done by your people. honestly, he is only leaving one month early, and leaving mid month gives you more time to rehab and get somebody in there by april 1. if he left last day of april, you would most likely experience a one month vacancy. this may be a blessing in disguise, so use it to get someone in for april 1.

A more cooperative occupant who is less likely to trash the place or fight you in court.

A home includes a house, condominium, cooperative, mobile home, house trailer, boat, or similar property that has sleeping, cooking, and toilet facilities.