Get a Wacom Intuos2.
Sure they're older than the new Intuos3 models. But I still use one every day to draw with (here's an example: http://homepage.mac.com/favoritestudios/Sites/nobyl/index.html)
I have a small one and it does everything I need, they call it a 4x5. Here's a link to an Amazon page that describes it:
http://www.amazon.com/Wacom-Intuos2-x-digitizer-electromagnetic/dp/B000060PEU
The things is, they don't produce the Intuos2 anymopre, so it's generall yout of stock. But you can find them cheap on eBay.
There's one on ebay right now for $1.04 and 2 days left.
So for less than $100 you could be in business. (And believe me, you will NEVER regret having a real Wacom tablet if you are drawing on the computer).