Now I also know that even though this property is currently zoned as Residential, it was zoned as Commercial before that and is also designed as a split. 

Why do you buy units where utilities are not split?

I've listed below the order I plan to attack things in, let me know if this sequence makes sense:Resolve excess moisture under house (minor grading issue, gutter required, possible plumbing leak)Repair minor roof leaks (repair flashing, seal leaks around chimney, replace tree-damaged shingles)Trim trees away from houseInstall 50 concrete piers and level foundation (foundation had work done previously but shifter due to excess moisture)Install vapor barrierAdd structural roof support beams in attic, add insulationRepair rotten siding/soffit/window frames (mostly upstairs)Repair porch (replace rotten boards, sand & paint)Paint exteriorInstall central AC/Mini-split system (any recommendations on this?)

The standard split generally works 3% each way, with the broker & agent splitting 1.5% (on a 6% commission).

Any ideas from splitting and flipping a house with my parents, to taking a loan on a two bedroom and finding a roommate?

(never stop negotiating - ask for buyer incentives - the furniture, car in garage, money back at settlement, possession - delayed settlement - subject to existing financing - offer a hybrid arrangement, financing secured by other property, no interest mortgage - split note financing - re-fi for take over/assumption)Always consider second stage negotiations for price reduction (give good reasons - exposed repairs after inspection - other issues found)Use safety contingent clauses in the event 3rd party assignee is not locatedSince you are doing your due diligence this target building - you should look for expired listing in the area and make offers on them also.

For the schedule E, I’m assuming that I’ll be splitting the 4/5th remaining mortgage interest and r/e taxes with my partner 50/50.

The commission split will not be the greatest, but make sure you get to learn all the basics.

They intend to split their inheritance (which would include whatever % of their ownership is in the condo) three ways between my brothers and I. 

They currently have a trust and have identified this property as being on it, in which case it would be split 50/50 between my wife and brother-in-law if my in-laws pass on.