If it's your own startup, you're screwing your cofounder by being part-time. The number of times I've heard a variant of "and they'll come on fulltime later!" i

If it's your own startup, you're screwing your cofounder by being part-time. The number of times I've heard a variant of "and they'll come on fulltime later!" is huge, and something that at least some investors I know of look at as a warning flag. If you're still in the mindset of "well, my corporate overlords will let me be tech lead for 3-5 years, and and and I'll get responsibilities and maybe even a career stepping stone" then you aren't in the right headspace to be part of a startup. Cut loose and let your friend find somebody who is mature enough (or dumb enough) to tackle that position of responsibility. The pay and benefits will be waaaaaaay better, in all odds, sticking with the corporate job. You will grow a lot more and learn more seriously pursuing a startup, and nobody worth anything will think less of you if that's on your resume instead of a corporate gig.