Thank you very much for that.
you are right, it is not anything typical.

I was an absolute beginner when I asked, meanwhile I have some more clarification.
Although I thought of it, the investor is not an investor in the sense of a startup.
Even Safe Notes do not apply here.

That part has been clarified in mutual agreement.
I appreciate any help, still digging in the resources.
Thank you very much.

This is an older question, but I figured I'd add my $0.02 while I'm thinking about this one...

It sounds like the real issue here is that the relationship with this “investor” was never defined. The phrasing you used -- “participated to accelerate development speed” and now “taking care of marketing and customer acquisition” -- makes it unclear whether they actually invested cash, paid for development, or simply stepped in operationally. And that’s the core problem.

If they financed development but no terms were set, that’s already a structural mismatch. When someone puts money into a startup, the norm is a defined instrument: a SAFE, a convertible note, or a priced equity round. That documentation would state their ownership explicitly. Without any of that, you’re left guessing at what they expected in return.

Now they’re also handling marketing and acquisition. That’s not an investor role. That’s an operator role, or an advisor role at best. Again, two totally different categories with different norms for equity.

There’s no “common” equity structure for someone who both funds part of the build and then starts doing operational work without a defined title, scope, or agreement. The only common thing is that this is usually handled before any of that work happens.

You need to start by defining what this person actually is:

• If they financed development, that portion should be formalized as an investment instrument.
• If they’re now taking on marketing and acquisition, that portion should be formalized as either a contractor role (cash), an advisor role (fractional equity), or a part-time contributor role.
• If they expect ongoing ownership tied to active work, then they’re not an investor at all. They’re trying to occupy an undefined hybrid of investor/operator, which is how messy cap tables get created.

The right next step isn’t asking “what percentage is typical,” because this situation doesn’t map to anything typical. The right next step is separating the two contributions:

• Cash they put in -- document it through the proper investment instrument so you know exactly what equity they bought.
• Work they’re doing now -- decide if that’s advisory work (very small, vested equity) or actual operating work (salary or a more meaningful but still reasonable amount of vested equity).

If you lump these together into a single percentage, you’re going to overpay for one side and underpay for the other.

Once you define those pieces, the equity question becomes much easier, and you avoid locking yourself into a structure you’ll regret the first time you raise real capital.