To be perfectly honest you earnings can be limitless, it just depends on how much time you are willing to put into taking surveys.
Most of the time you will earn between $20 and $75 for each survey that you take. And surveys usually take between 10 and 30 minutes to finish. It's really easy and it pays well for the small amount of time it takes to actually do it.
If you have quick hands and can type and read at a decent speed you can easily earn a nice income with paid surveys.
I use paid surveys to supplement my income all the time. There are many who also make a full time income using the kit to earn real cash from surveys, though.
Be sure to check it out and happy earning!