[throwaway413]

Without more detailed context, I'd say you are looking at a range between this comment:

> According to [1] 1-2% is common but IMO too low. Ask for 5%, settle for 3+%

and this comment:

> I feel you’re closer to “somewhat co-founder” status if you’ve contributed to major milestones over 5 months, especially without pay and no major investment. Assuming you’re negotiating pre-money and you’ll get a non-competitive salary; id like to see at least 10%. Consider you will be diluted very soon.

Anywhere from 3% - 10% I'd say is a reasonable number, pretty much depending on who's the better negotiator.