But even your example wasn't that. Your examples was -100k and +300k (or more), but offset by time slightly. That's still a very large net positive, just gated by a period of net negative.

I suspect there are some details that you are missing as to the situation of your friend. I know little about investment vehicles, but I've filed taxes at one point and paid them at a later point many times. For income taxes the rules for this are clear, and the amount you pay in fees and interest is also very clear. For some investment vehicle, I would bet if there's some taxes that need to be paid prior they have automated processes set up to pay them for you and take the amount out of the later payout, for a fee. If not, I can't imagine getting a short term loan for that would be too hard, even if you have to use private money (a real investor, or even just a friend).