I don't know about Stampin' Up, but I can share my experience and information about Close to my Heart.
I joined CTMH in August of this year because like you, I needed a way to get quality and coordinated supplies at a discount. I love it! It is a very small investment to get started; only $49 to join and get the basic "Essentials" kit. Then if you purchase/sell $300 or more per quarter all your product is at a 22% discount. If you only purchase/sell $100-299 per quarter you still get 10% off.
I'd be happy to answer any questions that you may have about my experience. My email is email@example.com
**Edited per board rules. No advertising/links.