They may be making assumptions and are looking to get the services from the other. 

I don’t see the sense of one of the partners almost completely expending his personal HELOC while all 3 of the partners are on the hook to make his payments of principal and interest while operating on the assumption that the house could appraise much higher in a short period of time by doing what may amount to putting lipstick on a pig.

Just an assumption of course. 

So, we will need to make some assumptions. 

(If you do that, I've found it's often helpful to highlight or group together, key assumptions you might want to tweak, such as assumed rents, or assumed interest rates, etc.

I would validate your rent assumptions with true comps (not just advertised rents) and find out what the bad debt and eviction rate is at those comps. 

(from speaking with people and reading reviews online)If someone here has experience in this area, I would love to hear your thoughts to validate some assumptions we have so far:Our first goal (rent it as short-term to make cash flow positive) is the most important one, we would even drop goal # 2 in years that we are not performing as good as we would expect.

I don't know what your assumptions are for capex, property management and utilities but for a historic complex I would recheck those numbers and check the cost of windowsand other things as they may be much more costly as they are in a historic area and may have to meet those requirements.

Sounds like a decent deal if your assumptions are correct.

With an average of 30.2 days in a month, and our previous assumptions, the monthly inflow of cash would be $1,132.50 (30.2 days x 0.5 vacancy rate x $75 monthly cost); with more ideal assumptions (30.2 days x 0.7 vacancy rate x $100 monthly cost), the monthly inflow of cash would be $2,114.