I believe (do not quote me on this) you need to present architectural drawings for both neighborhood approval and city zoning for permission to change the zoning from apartment to condo. Once you get approval, it would be a good idea to get the condos qualified as FHA approved dwellings for an easier sale. You will have to be given different tax id's for each unit and you may want to apply for a tax abatement if you will be making significant improvements.
I know my answers are a little vague. I can put you in touch with my husband Chris who has a better grasp on the process.
My 2 cents: I know that Philadelphia has a lot of condos for sale right now. It may be a better plan to look into the condo idea for the future. Once the condo market inventory has leveled off a bit in a few years, you may be able to yield more money from your conversion.