I think co-founders should have at least 10% equity, but you might give up to 5-10% to a first employee (depending on a lot of factors.) I guess the line could be somewhere around 10%. I would say that equity is the most important thing to get right, but titles are also very important and can change a lot of the interpersonal dynamics in a startup.

[1] https://www.cnet.com/news/tesla-motors-founders-now-there-ar...