10% isn't unreasonable for what you described. You'll learn a lot from them by being involved, it sounds like. And again, it's a long shot as with any startup

10% isn't unreasonable for what you described. You'll learn a lot from them by being involved, it sounds like. And again, it's a long shot as with any startup. My startup has offered 2% pre-dilution to a coder who will put ~200 hours into a project that already has about 800 hours on it. So he's putting in around 20% of the code. Dunno if that helps you, but that's what we're doing.