So you need something right now, but you're on a tight budget. Personally, I consider a tight budget to be $500 or less when it comes to portable computing. Even that's a bit high nowadays, but lets roll with it. I'm mostly going to address new products. Refurbished are an option, but my experience with them has been hit or miss. I will say that I've tended to notice any serious issues within the warranty period. I'll also note that I've never paid for a laptop. People tend to just give me old or broken ones for free, which I then fix up and use. It's old tech, but if it works, it works ^_^
For $499 you could get:
A new Retina iPad
A new Core i5 Windows laptop
Now obviously that's an apples to oranges comparison (no pun intended), because an iOS tablet and a Windows laptop are different devices meant to be used in different ways. Still, the dollar figure is the same, and that's how you should look at it; be brutal in your assessment. In my work, I've handled dozen of Lenovo's G series laptops, and I've seen how they perform in the field. No, they aren't bullet proof. Yes, they will hold up for years with even basic care, eg. not eating or drinking over them and transporting them in a padded case. The exception are the G570's, which have a poorly designed hinge that breaks way too often; stay away from those.
I'm not endorsing Lenovo, by the way. I just have the most experience with that brand and the lower-end HP's. The point is that most laptops you buy at this price point will be good machines. I get the argument about the durability of all-metal construction, but reinforced plastic chassis will last several years with proper care. Let's move on.
For $399 you could get:
A new iPad2
A new Core i3 Windows laptop
Again, same story as above but at a different price point. For the cost of an (admittedly nice) tablet, you could get a full blown laptop. Lets delve even further into budget-land.
For $199 you could get:
A new Nexus 7
A new Chromebook
And so we arrive at our final destination. You might argue that a 7 inch tablet (certainly a good device for web browsing and media consumption) is not suited for text heavy document creation. I would argue that (as with the iPad) it depends on what sort of documents you need to make. If it's limited to essays, a bluetooth keyboard should suffice. The only trick is printing, and that's true of most tablets.
Chromebooks are highly limited, to the extent that it makes more sense to look at them as tablets with a keyboard. There's limited file system access, application support, and printing support. They don't even support some basic web plugins. Still, you've got your internet, a keyboard, and your google docs for $200, and it makes a nice secondary machine to keep around when you do eventually land a high-paying job and buy that retina macbook pro ;)
I'm sure you're already aware of the sorts of products sold at these price points. I just wanted to lay them out, since I'm seeing are a number of helpful forum members suggesting macbooks. I don't feel like that makes a lot of sense for you if you need something right now and you're on a budget. Even if you like the design of apple products or the feel of OS X, those should be secondary considerations. I think if you can put up with the tradeoffs a $200 tablet or chromebook could work. Otherwise budget for $300-$400 and just get a well-review budget laptop. If you hate windows, throw linux on it. It won't be the same as a macbook, but my assumption is you'll appreciate the extra cash.