Newbie looking to purchase a rental in Philadelphia

[Cookie Ellis]

I am interested in purchasing rentals in the Philadelphia area.  However, there are sooo many "rules" in the city that I am a little apprehensive.  

There is a duplex that has caught my interest that is currently occupied with long term tenants on a month to month lease.  I could get slightly more in rent, however, is it worth it to maybe loose a long term tenant?  I will be seeing the property this week.

The property also has an attached garage that I don't believe the current landlord is charging the tenants to use.  

I don't want to start off a new, hopefully long term, relationship with a sour note.

P.S.  I haven't seen the property yet.  I will be visiting this week.