@malgorithm's answer is fantastic, just wanted to add some side-comments...
> How am I assured [?]
You're not, even if they start making money. Sucks, but true.
> You guys should be taking my money
One way to pay, if you want to help ensure their success & longevity, is to evangelize for them, and get other people hooked on their product. Getting other people hooked on it like you are and seeing the potential and get over the adoption humps... that's valuable! They're not taking money because it raises the barrier to entry, and growth is most important. Pay them by helping them grow.
It's valuable, but not in the capital sense. Each person you get hooked on their product increases their burn rate, and both makes them more attractive as an acquisition (which is scary for users) and more desperate for cash (which makes acquiescing to acquisition more tempting).
Without a road to profitability (or at least a road to revenue) even attracting equity is difficult; investors who enter with that knowledge will be looking to exit through acquisition, since that's basically the only way to exit, other than just getting more capital.
> How am I assured [?]
You're not, even if they start making money. Sucks, but true.
> You guys should be taking my money
One way to pay, if you want to help ensure their success & longevity, is to evangelize for them, and get other people hooked on their product. Getting other people hooked on it like you are and seeing the potential and get over the adoption humps... that's valuable! They're not taking money because it raises the barrier to entry, and growth is most important. Pay them by helping them grow.