Am I allowed to put ads of my own on my forum?

1. Am I allowed to put ads that belong to me on a forum that I administrate?
2. If not, am I still allowed to put ads but use the ads to put profits as contest prizes?

1) No, Forumotion has a contract with Google for the ads
2) No, That is how you get a free forum

You sure? My friends have done it on their forums.

Will you could pay remove ads then add them I would say

You first need to remove the ad's by buying ad removal and then going to Google Ad's and getting the code and pasting it where you want it.