the industry standard for print design software is InDesign
http://www.adobe.com
http://www.adobe.com/products/indesign/
if you or someone you know has a student id card, you can get the software at a very low price. it is quite intuitive if you know how to create documents for print.
if you don't, check out the community college and their continuing education department. ours here in san diego has tons of free computer classes covering the most popular applications. you may have something similar in your area. if they have InDesign installed in the computer lab, you can use it there for free.
i recommend InDesign, because you will be able to create your files in a manor which the printer requires, and not have to pay them for a lot of extra fix time [like if you use word]. additionally, i have learned from experience that it is important to use the best tools we can. they ultimately make the job much easier.
because these fliers will represent you professionally, i understand the importance of this decision.
best of luck.
- sabrina