If PA state statutes are old and do not address as many things as other states do; and, if PA courts refer to other state statutes when deciding lawsuits - it sounds like a full understanding of the current status of landlord tenant law in PA requires knowing the common law rules.
This means:
1) read the statutes - if a statute addresses your question directly great - thay MAY be the answer
2) read any case law addressing your question. If the statute seemed to answer your question directly the common law (or case law) rule could have changed what you think the statute says. If the statutes do not address your question, then the case law very well may give you the answer.
3) make sure any case law answer to your question applies in your jurisdiction.
Note about jurisdiction:
Jurisdiction means a certain geographical area (for this conversation anyway - there are times when jurisdiction doesn't refer to geography.)
The size of the geographical area depends on a number of factors. Each state has different nomenclature for the following information - I am using the nomenclature used in the state of Ohio....
If a case in the Supreme Court of Ohio decides a matter and has not been overturned by a federal court, a more recent ruling by the Supreme Court of Ohio, or by a more recent statute directly on point (which means you shouldn't be looking at this case anyway) - then the case controls how this matter works throughout the state (generally speaking)
If the Supreme Court has never addressed the issue, then look to one of the Appellate Courts in Ohio. If a case in an Appelate Court in Ohio has addressed the issue, this case controls within the geographical area covered by this specific court's jurisdiction (which is 1 or more Ohio counties depending on which Appellate Court) - unless a federal court has overturned the decision, unless a more recent Ohio supreme court decision says something different (which means you wouldn't be looking at this appellate court decision anyway), or a more recent decision in the same appellate court decided something different, or there is a more recent statute enacted that governs this matter (which means you shouldn't be looking at the appellate court decision anyway).
If there is no case in the supreme court, or your appellate district, then you look at the Common Pleas Court of the Ohio county where the rental unit is located. If you find a case at the common pleas court, that answers your question, then there you go - unless there is a more recent decision that answers the question, or (insert all the other higher courts or statutes here, etc....)
Now, what if there is no case addressing your question in your appellate district, but the question is addressed in another appellate district in Ohio? You can use that decision as an argument that it should be the same way in your appellate district, but this is known as "persuasive authority" not "controlling authority". Persuasive authority may persuade a judge to rule the same way - but it does not require a judge to rule the same way.
And the discussion continues and gets more complicated as we go on.
SO - I recommend if you ever have questions about what you can or cannot do - you look for any kind of landlord tenant reference book published by a reputable publisher that is addressed specifically for PA and is a current publication; OR, consult a local attorney knowledgable in these matters....