If you plan to do more BRRR's in the future to reach a certain goal, having an established HELOC that you can use as a credit line as @Christian Manhard was describing will continue to be beneficial.

Now my question is, should I establish a corporation entity for my rental in order to claim the business as additional income?

The summary is, although RS3 zoning is primarily for single family homes due to the code restrictions, when the building already has a second unit established legally, it’s grandfathered in.

You are not responsible for repairs, you should be listed as an additional insured under an insurance policy in their names (establish minimum coverage in your contract) You are not liable for anything, you don't own the property anymore.

That means you establish the financial criteria you "need", not "want", based on a plan. 

Buying for appreciation is a gamble.

New investor moving down in philly, and hopefully to establish banking relationships.Thank YouAbou

Many units in the area were converted before zoning was created ~1950 so if you can establish that the unit existed continuously from that time then you would have a legal duplex.

I know people do it, so it can be done, but especially in a multiple replacement property situation, it's a gamble!

Condos in established neighborhoods.