Hey Jonathan,I found contractors through refferals and facebook groups, those contractors were great but they are not experienced in new construction; plus with me being out of state it would be ideal for me to hire a GC, instead of sub hiring ( i dont have time for that being far away),I am switching from rentals and fix and flips due to there's just more profit when doing new construction, and way more deals!

While not impossible, you'll be paying a much higher interest rate for the loan than with 20%+ down and also you're likely paying some points or splitting the profit if for resale. 

Which is more profitable: an assignment or a double close, and why?

If syndicator is building reserves for the first year of ownership, for instance, and not paying distributions, AND recognizes rental profit, you will have a larger tax bill that year, since you "made money" in the IRS's eyes, even though you did not receive any cashflow from your syndicator.On a more general note, a preferred return does not mean you will get that amount of cash flow each year.  

If you can buy something habitable, and rehab it over time while you live there, that could be a home run of an investment when you look at your return on investment, especially if you house hack.Sure you may leave cash in the deal, but if you buy right, it could still be an extremely profitable and low-barrier to entry way to get into real estate.

And many are very profitable with scale.  

Interest only loans allows them to get a goal profit of $500-$600 per month per property.3) Each acquisition would require 20-25% down at an 80-100K purchase price. 4) Closing costs, and the Eric Spofford turn-key transaction fee of 10K would be in addition to the down payment and were not included for the purposes of calculating the cash-on-cash return.

If they talk about "halting distributions" to investors to focus on future business growth and profitability, what is their actual business plan?

I agree with Jaycee, but be cautious with other organizations having a "master lease" on your property.

If it pencils to a 25 to 50% profit or COC don't do it.8.