I can't say for others but for Upwork is not that bad. You do need to grow your profile with successful jobs to be able to charge more later, so start lower but do make a polished profile. Show lots of projects, including those from open source, if you have any, and fill all fields as well. Also state that you're at beginning and you're going for low prices only to establish your reputation. Also don't give up, keep on bidding on jobs even if it looks like a number game. In the end if you're persistent enough you get your break and can start build your clients base. After that it's a breeze, given you're indeed good at what you claim. Otherwise, it's a harsh environment for those trying to scam.