What are common red flags that an online job or gig offer is a scam?

Applying to a bunch of online work listings and some feel off but I can't always tell why. What should immediately make me suspicious?

The recurring warning signs: you're asked to pay anything upfront (for a starter kit, software, background check, or "training") — legitimate work never requires you to pay to be hired. The pay is dramatically higher than the going rate for the described work. Communication is sloppy, vague, or full of errors, or happens entirely over a messaging app rather than any verifiable channel. The employer or client can't be found anywhere else online — no real company site, no reviews, no employees listed on LinkedIn. You're pressured to decide or start immediately. And specifically for online "jobs": anything involving receiving and reshipping packages, or being sent a check and asked to send part of the money back, is essentially always fraud. When something feels off, a quick search of the company/person's name plus "scam" or "review" catches a surprising number of these before you lose anything.