Ii i write a blog and it gets published soon, after how many days can i get ads to be pasted in my blog.
Assuming that you already have an AdSense account, you can start posting those ads as soon as you wrote your first article.
there are lot of options....PPC,CPM,Affiliate marketing and so on....check other forums on this website for details. You can try affiliate marketing till the time your blog is not approved by PPC/CPM providers. Though few like adbrite approves very quickly
placing ads can be done right away, to make them generate real revenue is another issue, you should have decent content, backlinks, and of course traffic
And if you do want Google adsense, you HAVE TO HAVE a Privacy Policy page on your website or it won't be accepted. Just do a search for "google compliant privacy policy page" or something like that and you'll find one.