im not looking to buy any more domains so was thinking of using a sub domain does this effect its se results etc and how does it all work out in regards seo etc
Your idea is cool, but the thing is that your main domain will always anchor the sub domains, so that may pose a problem for your seo work.
it can work sub domains also get the higher pr then the main domain its depends how the links the being developed
Yes u can achieve ur targets with subdomain name also , i have seen many blogger earning $1000+ per month on sub domains on blogger.com . But if you have ur own domain name this helps you to get good sponsors . They go for good and nice names also .