If you are looking at a new or rehabbed property it may have a tax abatement. Tax abatements run for 10 years. When you look up the property on the BRT site you will notice an exempt amount on the property information sheet. If you would like to know more about abatements go to my site at ; http://www.phillycondo411.com/tax-abatement-info/ Also the BRT site has some detailed explanations of exactly how abatements and the abatement procedure work.
Ther is also an appeal process if the taxes have been incorrectly assessed BUT hold on. The BRT is in the process of being abolished and replaced by a new property tax department in the City. Eveything will change.
There is also a long standing proposal to shift all taxes to a new market price based system. They haven't figured out how or when that will be implemented.
Right now in City Council there is a debate going on to raise property taxes. The City needs money and property taxes will almost certainly go up but by how much?