It is probably possible, with the heating arrangement, to separate the three apartments into separately heated zones with their own thermostats -- it may even have been done already.

They like their color palettes and vignettes arranged on the fireplace mantle.

I'm saying it's 25/75 per a private agreement and how my parents have set it up in their will as well but for all intents and purposes, could we treat this as a 50/50 arrangement at least when it comes time to sell under the same circumstance?)

I arranged insurance through Liberty myself the last time I used them.

I have an arrangement with my friend where I stay with him one or two nights a week for cash, and his air went out.

At this time in the pre construction period, I may have given you 40-60 hrs of my “free” time to arrange this proposal. 

Property management and cleaning is key - since you don't live far away, you can get away with managing it yourselves (communicating with guests, arranging cleaning, arranging repairs) but you need to find a cleaning service who would be available in the short turnover window.

@Joe BlowI would Eliminate that gray area that typically comes with those type of arrangements.

The 2nd deal was sold in October of 2019 and his net profit per our arrangement was $15K.

(older homes, etc,I'm happy to talk to you about it if you are nearing the time where you are able to buy-  ie- financing arranged or good down payment available.