If you go down that path, make sure you weigh in the fees. 

I suggest building up some cash either by wholesaling or your job HML will only charge fees that could be put in your pocket. get the experience in first before you start flipping with your own credit you will not be upset.

I wanted to see if anyone had any experience with negotiating the fees, interest, and penalties on back property taxes in Philadelphia.

What kind of monthly fees or deposits do you charge?

Your property could become a super-fund site right along with the gas station.To me, #1 is a minor factor, if a factor at all.

A few factors here... are you doing the work or subbing it out?

There may also be non-monetary factors to consider, such as the family members expected rate of appreciation for the property and tax considerations. 

I recently looked at a duplex and wanted to get some thoughts on if these items should be factored into the offer price:The water heaters were over 10 years old, both gas furnaces were over 10 years old, the water was not separately metered, the front porch (cement) had some cracks in it, and both units would need some paint and new carpeting. 

But this is only after you factor in ALL the assumed potential expenses.

It depends on a lot of factors.