This blog used to be a blogspot blog before i decided to buy my own domain which means the link or URL to this blog changed from blogspot.com to my own domain. Every time you change the URL, you also have to change it in the sites you have submitted it on, which means, it is considered as a new blog. So, you go through the process again - getting your blog reviewed and get approved before you can accept paid opps. So if you old blog has already a PR and you decided to change it, you would lose that PR that you got even if it is actually the same blog, only the URL changed. It takes a lot of thinking and assessing if you arfe planning to buy your own domain for a blog that has already got approved and specially if it has already a PR. On the other hand, a lot of advertisers prefer blogs with unique domain but not all of them do so you can still make money even with a free domain like blogspot.com, bravejournal,com and a lot more.