Also, would I be able to borrow enough with the new mortgage to rehab it or is that usually with borrowe money like credit cards and smaller loans?

Don't get involved with the mail, tell old tenant to complete a Change of Address card at the post office and the mail will forward just fine.

Key card Access for my unit  is managed via front desk so I can't just give a key to sneak them in.

Impossible, try couple dozen, plus paintings, plus vices, plus couple tens of thousand in credit card bills.

@Jonathan Roper Ive gotten a credit card not too long ago to start building up credit.

Try to get at least 5 cards, more if you can. 

I own many properties in Baltimore, houses and commercial units - almost everyday I get mailings from people who say they want to buy my real estate - I get post cards, handwritten letters - silly yellow letters with hand drawn pictures of dollars signs and stick figures of houses.We all at the office have a good laugh, we comment on how awful their attempt to get seller's interest in selling their real estate. 

I transferred my credit card debt with 21+% interest into balance transfer credit cards allowing me to pay off my credit card debt without paying interest (that would later negatively effect my credit score, little did I know, due to opening new lines of credit--C'Est la Vie!)  

You can always join a local credit union and apply or get some credit cards. 

So all of a sudden you have a decline in collected rents, your cash-flow sails out the window, you're paying 18% on credit card debt, and with lower equity you literally can't afford to sell the property because you can't afford the debt payoff and the realtor commission, closing costs, etc.