Oh and what's this about money for posting? 50 posts for a fiver!
I also noticed that you wanted to know about getting paid for posting post cards. I don't know what it is, but from experience, I would say that it is an affiliate link to one of those survey/competition sites where you fill in loads of surveys and enter competitions. any require you to send the answer on a post card.
I tried it a decade ago and never won anything, most of the surveys would not accept me for one reason or another like being married or location or age etc. I did end up getting lots of grief from the postman though. I was getting loads of free samples every day that I was claiming. I could have opened a Yorkshire tea shop at one stage.