I presume that you both own the house equally.
Since you both received this property as a gift from your mother, your cost basis in the property is the same as your mother's cost. You can increase the cost basis with any capital improvements you must have made to the property.
When the property is sold- each of you will report 50% of the sale on your tax return. The capital gain will be subject to tax to each of you. Capital gain will be calculated as 50% of sales price minus 50% of selling expense minus 50% of the original cost basis of your mother minus any capital improvements made.
Presuming none of you used this property as your primary residence - the gain will be long term and subject to tax upto a maximum of 15%. This gain will also be subject to tax in PA since the property is located in PA.
Let me know if you have any question.
Please note: This advice is provided with the understanding that all the relevant facts have been provided by you. Any change in facts might affect the advice given and hence may not be relied on in such cases. Nothing contained in this reply was intended or written to be used, can be used by any taxpayer, or may be relied upon or used by any taxpayer for the purposes of avoiding penalties that may be imposed on the taxpayer under the Internal Revenue Code of 1986, as amended.