Thomas has provided an excellent answer. That has been the experience of myself and some friends over the past years.
We are all retired or semi retired, so have the time to sit in front of the computer and try things like this. Not only kids like to earn money from surveys, eh?
But, in my many years of surveys ( and I am with legitimate groups ), I have made an average of $3 a month. My best ever month was years ago, when I actually made $10.
Since I do it for fun and to while away time, I don't have a problem with this low rate of earning; but if you think you can make money to live on, you will be extremely disappointed.
And one has to be aware of the many scams and ID theft sites. Most survey sites are really scams and theft sites because the legitimate ones have full memberships ( no one leaves - why would they? ) with long waiting lists. Only the scams troll for "members" on public forums and boards.