The apartments are clean, don't need anything and have good existing renters who want to stay. 

I'm a new investor and my knowledge of financing is still growing but the balloon element of the existing loan makes me nervous.

I would advise you simply allow the tenant to go M2M on the existing lease if there has not been any issues. 

Everytime I look for Multi-family it either seems over priced or non-existent.

Repair existing rear deckwhich consist of replacing board on rails and decking and secure deck properly from moving.3.

Existing properties in NJ may be 1031 exchanged at some point in future.Thanks in advance for the help and Happy New Year!

An LLC is a legal entity that doesn't exist at the federal tax level.An LLC can be taxed as a Disregarded Entity, Partnership, S Corp, or C Corp based on number of members and elections made.An S Corp is a federal tax status (that many states also follow) that doesn't exist in the legal world.An LLC taxed as an S Corp vs a corporation taxed as an S Corp is the exact same at the federal level (there are potential state differences).

We purchased the distressed property as a Subject To, taking over the existing mortgage payments.

Whole sellers exist for a reason.

A lot of questions here...As your dad has a 50% interest, and a trust owns the other 50% of which you and your two siblings are the sole beneficiaries (I presume), it might be advisable to, after the trust interest is distributed, to have your father, you, and your siblings contribute your interests to an LLC in exchange for shares of the LLC (usually called "units").The property would be re-titled in the name of the LLC and the LLC can use it as collateral for a loan.It's usually highly advisable to engage an attorney to draft an operating agreement in this scenario to get everyone on the same page about ownership interest, who is/are the managing member(s), what happens when someone wants to sell -- do the existing members get 'right of first refusal', what happens if a member passes away, etc.