Man, I wish I could give you a simple answer but, there's so much to wildlife photography.....
That "affordable" part, whew.
At the most basic level I would say an SLR, (nowdays digital), and a long lense, 200mm at least, 400mm better, add a teleconverter, multiplier, extender (whatever) which will cost you some speed but can give you more "tele" on the cheap and that should get you started.
Actually, my best advice would be to do a search for "wildlife photography" or "learn wildlife photography" and dive in to the deep end of the pool. Once you have a good idea of exactly what you want to do, and how you want to do it, you can decide on your "system" needs. Hang out at some wildlife photography forums and look for camera/lense reviews in your price range.
I'm not trying to discourage you (at all), it's been a passion of mine for some thirty years now and I'm still learning.
That's probably not the answer you were looking for but I hope it helps some.
