How many times can you apply for adsense?

I don't think there is a limit on the number of times you can apply. The point is, figure out why you were denied and fix that problem and apply. It will not do you any good to just apply again, you will get turned down for the same reason. Fix that, and then reapply.

Easiest way to get approved is to use a Blogger blog and apply at the section where they ask you if you want to monetize it. Just apply through their interface and you should get approved in one to two days, more than likely.

BUT, if you do apply that way and get your number, you can use it on any site you build. But, if you build sites that don't conform to Google's TOS, they will ban you. So make sure that you have content, an about page, contact page, privacy policy. I think that is what is necessary, but don't take my word for it, I am not who you answer to, and I am not even sure that I know everything either.

Good luck.

I submitted multiple times. Just got accepted the other day.

I guess they have some strict rules regarding putting adsense on your site. I think it has to do with the number of outbound or affiliate links on your page.

I built 4 websites and they finally accepted the 4th one.