They are not hiring a founding engineer because they want to do something nice. They've probably realised this path is cheaper than hiring an external software development company.

Don't think for a second that you will be an equal in this relationship. You will be at their beck and call. You will be forced to write bad code to get early sales.

You'll get paid less to do more. I would stay where you are.

If they aren't willing to match your current salary and give you a much bigger slice of equity, I would decline the offer.

Practically and fiscally speaking, it's a bad choice. I made the same choice at about the same point in my career. Nothing came of it in terms of exit, and I learned a lot about my own deficiencies in the process.

The benefit of being young is you generally have fewer obligations tying you down, so this kind of risk is palatable. You just have to decide how much risk is worth it for the experience; put a value on that intangible element experience.

Is the experience and sliver of opportunity worth $90k + work-life-balance?

1. "It's better to regret something that you have done instead of something that you haven't done."

2. "I want to retire comfortably with a high level of confidence."

People in my life always advised me to follow the highest paying job. I'm not sure that was the right advice given my circumstances. It's really up to you.

Second, keep in mind that most startups fail, so beside the financial upside that might never materialize, you should do it for the adventure itself.

Building a startup is an amazing experience, you might start building something and end up building something completely different, you'll meet tons of inspiring people and you'll put yourself outside of your comfort zone.

The question you need to ask yourself is, do you want deep inside leave this adventure or you prefer a comfortable salary and job security. Because it will be anything but that.

If you don’t control equity, you cannot control the outcome, value, or liquidity of it.

250k is good money. I'd stay, accrue experience and contacts, bank some money. The startup probably won't work out anyway - they usually don't. And even if it does, 3% equity is too low for the financial and personal sacrifices you'd have to make.

tldr: seems like the wrong time

I would take advantage of your present (rare) work-life balance to cast some of it to the wind and work for these guys as a consultant without resigning from your employer, as long as it is not a conflict of interest.

Even help them find someone in their price range with the confidence that you can still back them up as a consultant going forward.

You hope non-technical founders are good deal-makers, but underhanded dealing is all too common as well.

So deal. One of the sure ways to find out how honest and generous someone is. I would accept less than the 160K on the table this year but with equity in proportion regardless of being "only" a consultant who might end up building the whole thing anyway. But it would have to be $1000 per day and if it turned out to be 80 days the next year it only cost them 80K with no benefits. What a bargain so there's no excuse not to stick with a calculated 1.5% proportional equity in this phase of the lottery. And keep on going :)

That would be about my final settlement point, where you start and how you negotiate down from there you're going to have to play by ear.

The next best thing to being a founder is to be able to write your own contract regardless. You already have an employer-employee relationship, that just doesn't sound like an ideal kind of relationship when it's going to be functionally a 3-person startup of "equals" the minute you start building.

Have fun :)