It all depends on the circumstances. Is "early-stage" mean they have $1m in the bank, or $10m, or $100m? Do they _need_ you, or are interested in a hire?

I think if they're early stage enough that you might get 10-20% (btw, 10% is optimistic), then there's no cash available (apart from a small signing bonus like 10-20k).

But really, you need to talk through the actual numbers with someone who has been more of an idea. Do you have advisors? If not, happy to help: my email is in my profile.