Gherkin is always nice, and mockups, screen shots, etc.
I'm sorta overqualified to test the current Nostr projects, but I figure that they might eventually get bigger, and then my market would expand and I'd already have customers.
You could also scale your service offerings and rates to the size of current Nostr projects and build up a clientele in the early days.
A service like this is actually a boon that would enable more lone wolf Nostr devs to bootstrap innovative projects more effectively.
Yeah, the prices I named were for something larger or more complicated, like Highlighter.
For someone with a smaller project, I'd probably also do more design/workflow work and help them market. I have a powerful npub.