Monetizing with surveys

Hi guys!
I hope I am posting in the right place, in case feel free to close or move my thread.

I would like to add a survey-system on my site, so that I can monetize everytime some visitor complete a survey through my site. From your experience, what are the best solutions for surveys? I mean, considering several aspects (how easy is to enter the network, how much they pay per survey completed, etc.) what site would you suggest?

Thank you for your help!

Monetizing site with surveys , then Videos is the best option .

Have videos on your site and lock them with Surveys

or sites like Downloads and lock the Download Links