other coops like at 18th and JFK are not market based and you have to sell back to the coop when you leave/die at very reduced rates....so, perhaps you have heard of 1919 chestnut which is realtively new to the market.
I am reading behind the lines when I suggest that Co-Op properties (Shared Ownership) are generally not a option for the broad market; Center City only has only several, nothing like NYC. However, many previous apartment buildings, both small brownstones and larger facilities, have been gradually 'converted' to condominiums by their owners or developers. Sometimes individual units can be approached as a 'Lease Purchase' arrangement (Two Simultaneous Contracts) that are helpful to both the buyer and seller. Some very attractive studio and one bedroom options exist. Cash is king and will leverage a nice purchase price. If the building is approved for conventional Fannie Mae and FHA financing, the sales flow nicely. If you require addition details please contact me directly. 215.531.2000