Developer here + $5k investor ready. What simple business would you build first?

I'm a developer, and I have someone willing to put in $5k to get something off the ground.

The catch: he's not looking for a moonshot or some complicated startup. He wants a simple, understandable idea that can realistically start making money. On my side, I can build pretty much anything software-related: SaaS, automations, internal tools, scrapers, dashboards, AI wrappers, niche products, whatever.

What I don't want is to spend 3 months building something clever that nobody needs.

So the question is: If you had a developer + $5k + a goal to build something small but profitable, what would you go after?

Would love specific ideas, niches, or pain points you think are underserved right now.