Upload & Sell: On
Help- can I get by with 128 gb - instead of 256? My wife and I will be sharing and we will use an external hard drive too.
What Glass said, above, assuming you're going with a Mac?
Also, you need to Google up "free up space on Macbook Air" or "macbook pro" and you'll learn a few tricks to get rid of some "cruft" that hangs around on the system from a default installation -- optional of course, but it'll give you back a few GB easily.
Also, again if you go with the Retina, download SwitchResX if you want to work in Native resolution (you can also use the other resolutions, too)