You could go to your local library branch and checkout CDs and rip them to your harddrive.
You could go to allofmp3.com.
You could borrow friends'/family members' CDs and rip them.
Any number of ways if you really want to avoid buying CDs on your own.
Heck, check out used CD places in town. You can get new(er) CDs at places like those for a lot less than a brand new one.