I've never done any freelance jobs on this site, but I'm sure that if there were scam jobs out there that CGTrader would crack down on them right away. This isn't to say that there are no problems with the freelance jobs. Look through the forum and see the postings of some customers and artists that felt they have been wronged and want to call out the artist or the customer in a public forum to give warning to others to not use them.
Personally, I find the jobs oversubscribed. Some of the postings expect a complex job on a low budget and yet there are many artists who apply. It's a buyers market on here.