If I put Bidvertiser or another companies ads on my websites, will Adsense not pay me when I near cashout, is it illegal according to Adsense rules to do that?
You can use adsense in conjunction with other ads. Google does not bother as long as it is not mixed with the other ads.
You can use as many ads on your website as you like. I think buysellads only lets you use them though.
As per the google TOS, I believe the ads you're putting on your website, should not look like/similar to google adsense ads.
