Dreamstime sells quite good. 

There are quite rigid requirements of the image quality and composition.

There is no exam. To register you dont have to send a scan of your passport or other documents.

The minimal size of the image is 3 MP.

Dreamstime is selling photoimages, pixel, vector and 3D illustrations, and RAW-files.

The referral programme:

10% of all purchased and sold images of your referred submiters or buyers, during 3 years since the moment of their registration.

5$ as a bonus for putting the Dreamstime banner on your website (the website must be approved by the moderator)