I would buy past issues, for sure... not a HUGE lot, I don't have room to store them, and I've been getting rid of my magazines too. You might have more success on Ebay than a garage sale... but of course it's more complicated.
My library has a magazine exchange box where you can drop off old magazines that you don't want and pick up other people's cast offs. I love it! People drop off some great mags, and my scrap magazines are always picked up the same day, so someone out there is reading them! (and once I noticed that someone returned it to the box for someone else to read... yeah, I'm at the library a lot with the kdis!) you could see if there is a local cropping club, or library that will make them available if you can't sell them...