Oh $deity I can't tell you how many times I've run into this. Usually the "marketing" person has a comfortable 9-5 job and wants to do the startup work in the spare time available when not attending to work or family responsibilities. The technical co-founder, in contrast, will naturally be expected to work 40-60 hrs/wk (at least) for no salary, just some kind of usually-not-well-defined "equity", and not much of it, simply because she didn't produce The Idea.