I've been through this before (15 years ago). As a "first engineer" as well. I was fully-vested in a fair deal. The start-up had been acquired outright by a l

I've been through this before (15 years ago). As a "first engineer" as well. I was fully-vested in a fair deal. The start-up had been acquired outright by a large private co which gave a nice real world known valuation for the company and the new owners were entering a pre-IPO quiet period (we were told it would happen with few months). Exercising my options would net a 7 figure stake for at a cost of about six-months salary. I hadn't understood all the options complexities at the start but learned fast about this time thinking of selling some. Engineer #2 got a loan in order to exercise their similar options and got totally screwed as things slowly imploded. I never did exercise them thankfully. In another case my options as a early engineer (again fair enough terms) ended up actually worth actual money after a few rounds of dilution and conversions and sales ultimately to a public company. However it was a few K worth after 5 years of work on paper it had been variously valued up to high six figures. I know now that options are, as someone said elsewhere in the comments, "a variable odds lottery ticket".