What is a fair compensation (base + equity) offer for a product manager at San Francisco series B startup (100 employees)?
What he made at has last company (unless it was abnormally or structurally low).
You’re too big, and too middle-stage, and too well funded, to be expecting anyone to take a salary cut anymore.
By the same token, you’re still sort of a start-up at ~100 employees. Everyone can still make an impact, especially someone at a manager level. If someone expects a raise to join you … something’s wrong with that hire. Unless he was woefully underpaid or structurally before — which indeed can happen, that you need to fix. You need to pay fair. But expecting a raise to join a 100 person start-up is a flag. He won’t work out, at least not for too long — he’s doing it for the wrong reasons.
The harder part is getting equity / options right at this stage. At this point, you have so many employees, no one but a senior-ish VP can get a material stake. You’re dividing that option pool across 100+ employees already, with many more to come. All you can do is your best here, and be fair on a relative basis.