Shawn,
First off, good on you for thinking of your little brother. I remember flipping through countless gun magazines (albeit hopelessly) back when I was younger wishing somehow to be able to afford a nice hunting rifle.
My recommendation to you, sir, is that you take a HARD look at the the blued/walnut Ruger Model 77. This is a finely crafted rifle that will stand up to years of use. Not only that, but it inspires pride-of-ownership and bears the classic lines of fine American rifles. I realize your budget it tight, but since you can only afford to buy this once, and I'm sure you desire to achieve the greatest bang for your buck, you cannot go wrong with this rifle. I've seen them for less than $450 brand new at local stores (the ones with better prices). If you compare this rifle to the cheaper Savage/Stevens lines in person, you will note a huge perceived quality difference. While the Savage and Stevens are good guns indeed, they are more cheaply furnished (stocks and bluing especially) and not in the same class in this regard.
Because your brother will likely be using this rifle for years to come with hopefully many hours afield, I heartily recommend you take this small step up in price to gain this significant leap in quality. If you do, it will likely become something that he will treasure for years.
As far as the caliber, noting your brother's young age, I would recommend you purchase that .243 and ensure that he practices extensively with it before going afield. The beauty of the .243 is that it allows the ability to ensure correct shot-placement with young/inexperienced shooters due to the low recoil. As long as the shots are well-placed (as with any rifle), the .243 has plenty of power for the game here at hand.
As far as scopes go (to keep the rifle in your price range), I would recommend you take a look at the Burris Fullfield II. I've seen that one for as cheap as $150-170 around the web somewhere.
Best of luck with whatever you choose, and way to go bringing another young man to the realization of the great sport we have.
cox3497