You need to figure out a common ad submission format for your advertisers. Because you are launching a print publication, you'll need ads that are saved at a high resolution.
So you might ask them to save their high resolution ads as PDFs and pull the graphics out using the graphics tool in Adobe Acrobat, or you can ask them to send you a TIFF file or a high-resolution JPG, in this order of preference.
You might also want to consider postponing your business venture until you can purchase the basic hardware and software to get you started. Relying on someone else's system isn't the best way to start a business.
Question added to topic Marketing • October 9, 2008
How do I accept advertisments for my new magazine if I don't have all the supporting software?
I am creating the magazine in Microsoft Publisher, and some ads might be saved in Photoshop, for instance. I don't have the money to purchase all the software to accept so many advertisments. However, my business hinges on it. I'm starting a free publication driven entirely by advertising. I'm using Microsoft Publisher and not even that recent an edition: It's at the library. So do I have people send the ads as PDFs and then somehow cut and paste into a Publisher page. Or is it more complicated than that?