How do you feel about getting one used or refurbished? I'm a CS Student too and by far the most popular type of laptop on my course (bar MacBooks) is business grade machines like Lenovo ThinkPads, I use a T440s myself. They are expensive new but can be picked up used/refurbished easily for under $600, you could quite easily get something like a T450, T440 or T430 for that price (that's ordered from newest to oldest), Alternatively if you want something smaller/more portable look at things like the X250, X240 or X230. The benefit you get over regular consumer machines is far better build quality, better support and a wide variety of accessories and spare parts - You can easily get extended batteries that last 10+ hours for example. If you were to break part of the machine, for example one of the hinges, on many consumer machines it can be a total pain to find the correct part, with business machines part numbers are very well documented and easy to find. As an alternative to ThinkPads I'd also look at other business machines such as Dell Latitudes or HP ProBooks as these are similar in terms of reliability and build quality.
If you don't game, focus on ones without dedicated graphics, this will help your battery life and look at the screen resolutions, on larger screens (over 13") you're going to want to look for resolutions higher than the basic 1366x768 most cheaper laptops have, the higher resolution is particularly useful for having two things on the screen at once or if you are using some sort of IDE with loads of different panes. Your budget more than enough for an i5 so I'd focus on that or an i7, and I would focus on laptops that either have SSDs or upgrade it with one yourself, the performance and robustness improvements are immense.
