Their salary from a $DAYJOB?
This is made even worse by jurisdictions where employers can claim rights over side projects.
Pay the couple of hundred bucks to have a lawyer review your current employment agreements vis-a-vis "Intellectual Property" and let you know where you stand. If your employer has grounds to claim your independent work, negotiate a new agreement. If they won't negotiate, find a new job. Or quit and consult part time, or work as a short-order cook or barista while doing your startup... I doubt O'Malley's Irish Pub is interested in your startup's IP.
And, about side projects: work on them on your own time, on your own equipment, and don't compete with your employer. (And most importantly, don't brag to your coworkers about your moonlighting ventures.)
This is made even worse by jurisdictions where employers can claim rights over side projects.