That is a multidimensional equation, and compounded by individual tolerance to risk.
First off, what do you consider the odds are of this business plan becoming operational. Start from there.
Then come the personal additions to the equation, your cost, ability to absorb a loss.
I do not go past the first part of the equation, I feel very strongly that the business will become operational shortly,
So I dismiss the need to address the other issues, for myself only.
Hope that helps,
:)