Nick - First eviction? congratulations... these are always fun. Google is your friend on the laws on this one. Ive used KPMM to handle an eviction for me in the past. Its actually quite simple.
As for the one where the lease runs out - be sure you have a copy of the lease before you close - it probably says 30 days notice (although I have one from a previous owner that gave the tenant 60 days)... know the terms. Send it in WRITING, certified if you want proof, that your not renewing. If they stay past the 31st then you can file with the magistrate for eviction. This is where I personally would use a property manager of attorney that knows the nuances of the law.
Far as Im aware you inherit the terms of the lease until the lease expires when you buy the property, hence why I always want a "lease review contingency" in my contracts.
My last eviction cost $151 in filing fees in Whitehall at the magistrates office, case was heard 15 days later and we won. We were then waiting 10 "business" days to file for possession, however our tenant came up with all rent in arrears, the next month, fees, etc. - we decided to keep them, but may be again going through the process if they don't shape up quickly (can I pass this guy to you... especially if your going to have a vacancy soon :) ). Seriously, I wouldn't want anyone from here to inherit the guy.
One thing I do when making an offer is review all leases, but also review the tenant. YOu can search the PA judicial portal (Google that one), drill into the county and search for criminal and civil proceedings. Its a supplemental thing I do when evaluating a new tenant and I've found some good information on that site.
Personally, get a property manager to handle it. KPMM has been very reasonable for me and it completely removes the headache. Good luck!