To me part of the allure of a passive income project is being able to control more than just the technical aspects--to be able to define the customer-facing and business pieces too.

Perhaps more importantly, your chance of producing meaningful income goes up exponentially if it's a one-person show. A small startup has the overhead of at least ramen-level salaries for a few people, possibly an office or shared space. If they've taken seed money their investors will be pushing for growth over profitability or possibly even revenue. If you're doing a profit share, even in the best of cases it may be a looong time before there's any profit, even if there is meaningful revenue.

Every startup is a longshot. It's an even longer shot if you're taking a sliver of profit from people whose interests may not be well-aligned with yours.