...to put adsense into a new site? I think i read somewhere that search engines dont list you if you put up a new site an right away you put adsense in it? If this is true or there is a draw back to putting adsense too quickly, whats the right moment?
From the start. Also that listing comment is absolutely wrong. I've had no problems ranking any sites running AdSense. The search engines, if any, that do this are probably useless and not worth the trouble anyways. No drawback whatsoever to placing AdSense immediately, although if you're submitting to directories, some asshat directory owners will brand your site an MFA even if you have a great deal of valuable unique content. If you're building sites quickly though, you can ignore that minority, seriously. On that note: every info site I've bothered submitting to directories has received at least one "Declined, Reason: MFA" email. Excuse me? If you take away the ads, the unique content is still there and provides a valuable resource to people. If you blend your ads well, you won't be able to avoid these messages.
I don't think search engines even see that you have AdSense. They aren't programmed to look at the javascript code.