10x10 room in garage....need some advice

I am moving into a house at the end of this month, and my dad is going to be building me a 10x10 room in the 2 car garage for my music production. Mind you, there will be no live recording. My production is sample based, with direct guitars. Although, I would like to mix using monitors. What form of INEXPENSIVE sound reinforcement can I use in this room that will make it somewhat "true" in sound? After reading some posts, carpet is bad..... how about muslin (cotton fabric)...is there a cheaper way to put foam up? Any suggestions? Thanks!!

you have some reading to do http://www.saecollege.de/reference_material/index.html cheers john