I would like to know... could i go the a thrift store and get several sweater and recycle the yarn....
Sure, I've heard of many people doing this with success. Haven't tried it myself but here's a link to an informative tutorial on the subject http://www.neauveau.com/recycledyarn.html
Beware commercial sweaters
If you pick up commercial sweaters, often the knitted fabric is cut and seamed using a serger or sewing machine, and so you can't unravel the yarn in one long strand like you might be able to with a handknit sweater. So try to look for handknit sweaters that can be unraveled in such a way that the yarn would be useful for knitting.
I raised the question a while ago. If you'd like to follow that conversation, it's at:http://www.menwhoknit.com/community/?q=node/3800
I never actually gave it a try; hope to though. I just didn't find any appropriate sweaters at Goodwill. Maybe next time.
Grace and Peace,