Planning to have my own domain...

I am planning to buy a domain name in my 2 blogs but im still thinking maybe my page rank will be affected or you know.. Because my 2 blogs have a good page rank and they really make good money for my paid reviews. So, im still thinking about it, one of my friends says that I don’t need to buy domain name this time, maybe on this blog I can buy a domain because this one still new and no page rank yet. What do you think? I don’t want to make decisions right away because maybe I will regret it at the end. Im happy already with my 2 blogs femikey.blogspot and femikey07.wordpress. Some of my friends already have their own domain and its kind a interesting and inviting for me to make my own too. Oh well, will see what happens. I still need to figure it out before starting to get domain for my 2 blogs because I don’t want my page rank will be affected if I do that.