I believe you are trying to understand whether you will be taxed at the 0%, 15% or 20% rate on any capital gain you may have from the sale of this property. Even though your other income puts you in the 15% bracket, for purposes of determing the capital gain rate you must add the capital gain itself to your income. Since the next tax bracket for MFJ begins at $75,900 of taxable income, if your gain pushes you there then you are in the 25% tax bracket and thus the 15% capital gain bracket.
The above only relates to the capital gain portion. If, as Critter#2 suggests above, you have been renting out this property and thus have depreciation recapture to deal with, that recapture portion will be taxed at ordinary rates. This recapture provision applies even if you did not claim or get any benefit from the depreciation in prior years.
