Most mortgages don't allow seconds but honestly, the bank isn't going to check so you could roll the dice on that. 

Check out this article on BP https://www.biggerpockets.com/blog/multifamily-dscr-loans that goes into more detail.

BUT you have less red tape, no tax returns, DTI, or employment checks are required.

Almost every residential area is zoned for multi-family (I have already checked and verified this) it just so happens that most of the homes on the market are SFH.

I can still hold properties under check book SDIRA?  

My questions is: if the LLC collects money for admin costs, such as background check and other membership related costs and/or monthly membership for co-living environment, is it considered a "For Profit" entity or is it a "Non-profit"  entity.  

I’d also recommend spelling out explicitly the timeline or benchmark the team wants to hit before deciding if or how to exit the investment.

Further, if it is not spelled out in the guidelines it could be an case by case decision.  

I would check out Facebook Marketplace, Airbnb, and Furnished Finder to see how much other rentals are going for in your area.Mid-term rentals should be furnished and can rent for more than LTR.

You should also check out petscreening.com.