how do i find advertisers for banner space to generate income on a music social network i am having built?

[Peter]

i am currently having a music based social network being built and designed for me which should be ready for me at the end of february/beggining of march. I have requested that there be advertising space on the website that will allow me to sell the space to generate an income from it and help with the running costs of the servers and other general maintaining of the site. I am not entirely sure where or how i would go about trying to find businesses to advertise their products or even how much i should be looking at charging for this. There are many sites i hav visited about this and most just give you rough ideas of how to calculate it using a $/£ as the standard cpm rate. would any body be able to shed some light onto this matter with any links to sites that pay quite nicely. i am hoping to have around 10,000 users within the first 3 months if that is any help at all.

many thanks