PA residency and MD job

What is the name of your state? PA
I am looking to establish PA residency. Will the following documents
sufficiently prove residency or are other documents needed?
1. mortgage on an apt. in PA.
2. a PA driver's license.
3. a PA voter's registration card.
4. cars registered in PA.
Also, is there a document, or a set of documents that prove that I am, in
fact, a resident of PA?
I'm currently employed in Maryland, but I have a verbal agreement with my employer that I am to work at home 2 days a week thereby giving me 4 days (including the weekend) to live in Pennsylvania. Can such an arrangement work for the purpose of residency, and if it can will I still have to pay MD state taxes or will it be enough to pay PA state taxes?

Those documents will establish PA residency. However, you'll have to pay non-resident taxes to MD for the money you earned while in MD. Your employer will have to split your income into MD & PA. You'll pay PA taxes on all your income, but PA will probably give you a credit for the taxes you pay MD.