As far as your proposed solution seems like it should work in terms of getting you a “first position” HELOC.  

Grant funding can be up to 50% of total project costs of the proposed Development, depending on the need for assistance to create a viable development and adequate eligible project costs.

When I asked why a seller would ever accept this, I was told quite emphatically the property requires work and therefore nobody can obtain financing so the proposed terms were the only way the seller could sell the property.

Of course, your bid will be extremely important, but it would be a challenge to get to the point of executing a bid proposal if we aren't confident in much of the above items.  

They proposed higher than market rent, but want to keep 2 people from thee organization volunteers in one room in future.We checked the website of the non-profit organization, their program include several categories, including helping international children to school, housing for the homeless, etc.

Are there current regulations or proposed regulations in place.

You might have an easier time buying a parcel and subdividing it into residential and commercial lots, then proposing the commercial use variance just for the commercial lot.Doing all of this research on your client's behalf is mighty generous and very time consuming for you.

Thanks in advance for patiently answering my question.PS: I don't have a CPA, and I'm in the process of getting one, but I wanted to get a frame of reference so I can roughly compare notes with anything my future CPA would propose.

I think most locals are aware of the history of STRs proposals/cases in Portsmouth, Laconia’s existing restrictions limiting non-owner occupied STRs to resort/shorefront only, VT's local option tax that allows a 1% tax above the state's existing 9% tax, Portland cap on STR permits and increases tied to inflation, and it's also probably a good idea for folks to understand NH's Senate Bill 249, which proposed a "ban of local bans" around STRs and basically died on the floor(?)

When it comes to your "all you have to do", all I can say is that that is quite a bit of print as well and for the most part summarizes pretty much what we do, except we do it with less risk to the member than you propose.