Here is a link to the city / presuming you are buying in Philly / other area's will have the same or a similar process to obtain a certificate of occupancy.
You must have c/o should you plan on having the property occupied by humans for whatever the property is intended for / home / rental /etc.
You need an agent to guide you. In Pennsylvania the seller pays both the commissions for the buyer and agent representation. It will not cost you half of the commission to be fully represented, find a good agent. They will give you professional guidance based on the individual situation, which is very important.
Ana Barlow, Coldwell Banker Preferred
Avenue of the Arts Office - Philadelphia