Interesting! Can you share a bit on how you met this dev? Did you come up with this way of compensation upfront, or is it a deal you struck after some time working on it with him/her?
I guess the delusion I'm under is that it's possible to have the cake and eat it :) Large startups with seed money won't probably be needing my service under the conditions I described in the OP, and small startups will be struggling for so long that unless it blows up to become the next big thing (probably won't), the actual passive income I could get wouldn't be meaningful. Thanks for your input!