Due to our limited funds, we want to figure out how to get a great deal, with as little of our cash in the game as possible, to allow a "safety net" of sorts.

I like this one.3) Highest risk because too much carrying costs with hard money, inability to predict where market will be when it's time to sell (9 months + modular construction time), opportunity cost if your funds are tied up and another deal comes along so I'm not a fan, negative cashflow like crazy over a long period of time is no bueno.Like the numbers on your deal, too bad 9 months + build time is really far out.

Fund that Flip gives their complete history.  

The other factor is this  - If a contractor bids too low, then realizes in the middle of the project that he won't make any money, then you are working with a contractor that either is not a happy contractor, or they have to do other jobs to make ends meet on yours, maybe they even misappropriate funds.  

With 80% you would pay off your current loan, then keep the remaining funds.  

That sounds like a good strategy to wholesale deals to help you fund long term rentals.

What if the lender (in the future) wants to have a 70% LTV instead of 75% LTV?

Stock market is not a good place for money that your planning to use relatively soon and bond funds, CDs, and money market funds don't offer much ROI.

I want to put in an offer for a property, it listed on MLS for 120k, want to put in an offer for 70k but my agents said I would need the fund in my bank first.

They had held up my release of funds for over a week after signing while they waited for the invoice and then paid it and closed out my account the day they received it.