WHen you purchase property in Philadelphia, it is usually called "fee simple" ownership. That means that you own the ground and whatever is built on the ground...the house, for example. Sometimes there are situations where people own a home, but lease the ground. Many times the lease has a 100 year run so that people don't have to feel that they will be thrown off the land. There is an area in Southampton, PA called Bryn Gweled Homesteads. No one owns the land, but they do own their homes. There is also a similar place in Philadelphia near Pennypack Park, but I don't remember the name of the development.
This situation also occurs in certain communities where there is manufactured housing. You own the unit but lease the ground.
If you have any other questions, please contact me.
Carol Murray Cei