I agree with the other agents that have responded, first things first, check your loan documents. Most of the loans we are seeing are not assumable, however there are always exceptions.
Why not sell direct to the person you are considering will assume your mortgage? Rates are still at record low, and now there are great programs and incentives to qualify a buyer. It may be best for you to sell now so you can move forward. I would be happy to provide you with information on the current market value of your unit-email me.
Regarding the potential of renting, if you choose to hang onto the property, check with your association, or your condo decs and bylaws to see if renting is allowed. Some condo buildings allow rentals while other do not, this may help you determine your final decision. Best of luck to you!
If you are interested in hearing how I sold my last Forest Park listing in one day, email me, firstname.lastname@example.org.