Pretty much any drug store sells it... including Wal-Mart, Walgreens, and Target.
It's about $7 CDN, so I'm guessing $5 or so if you're from the USA.
For me personally, it lasted about 3 days before you could see the roots, but my upper lip hair was VERY dark and grew really fast.
If you have lighter hair, the roots wont be noticeable, so yours would probably last for about 2 weeks.
Facial bleach is even more effective when your hair isnt dark, so consider yourself lucky!
If you can, find the facial/body bleach by Sally Hansen, it works WAYYYY better than Jolen (you'll see the brands when you get to the store)!
If your hair becomes unmanageable and darker, I'd recommend plucking them off. It's more cost effective, but be prepared to do it for the rest of your life!
I've been bleaching since 5th grade haha, really dark hair but very pale skin. EXTREME experience!