Recognize this company is selling 25% of itself for $500k, meaning the entire company is "worth" $2m. I'd guess no one is going to buy OP's stake at these level

Recognize this company is selling 25% of itself for $500k, meaning the entire company is "worth" $2m. I'd guess no one is going to buy OP's stake at these levels, given that he's likely 1/3 of what the investors are buying already. If OP wants to, OP can not agree to any vesting agreement, keep his whole stake, and likely do significant harm to the company in doing so (of course I'm making some basic assumptions here, but I think they're fair, and about as good as we can do considering the lack of information). If OP does that he or she is actually shooting him or herself in the foot, and destroying the value of his or her own shares. I can certainly see many scenarios where it's actually in OP's best interest to give up more of a stake, though it's impossible to know without knowing what type of company it is, revenue and growth rates, etc. If we assume it's a software startup raising at a $2m valuation I would strongly encourage OP to play the long-term game, as the likelihood the stake will be worth nothing if he or she takes 33% off the table right now is remarkably high.