Hey Gavin,
If you haven't already pulled the trigger on your purchase, let me offer another suggestion.
I have a particular affinity for Badger airbrushes and have used a Badger Model 200 for almost 40 years. This was the first AB that I ever purchased (as a teenager - I worked all summer in a used car lot cleaning cars to earn enough to buy it), and one that I still use. Needless to say, this is good kit and will stand you in good stead.
Get a Model 200 start-up set with the small hose and Propel can, but also get the Badger Spare Tire Valve Adaptor, Badger part #50-029. This adaptor fits into the Propel Regulator (included with all the starter sets that have a Propel can), and allows you to use a spare tire from a car as an air source.
http://www.badgerairbrush.com/Acessories_5.asp Using a spare tire as an air source is very economical and aside from having to get it pumped up, works very well. I painted models for years using my Model 200 and a spare tire. You can even pump up the tire using a bicycle pump in an emergency. (Not easy, but doable - I spent several Saturday afternoons in my youth doing just that.)
In a pinch, you don't even need to get an "extra" spare tire to use just for air brushing, you can use the one from the family auto for a while. (A used tire and rim sould be a very inexpensive purchase, tho. You don't need a "servicable" tire with good tread and a really nice rim, etc, just one that will hold air. It may be ugly, but who cares as long as it works?)
Doing his might cost a bit more up-front (the Model 200 over the Model 250), but should delay or avoid the need to get an air compressor or to have to rely on the Propel cans (which are very expensive on a regular-use basis).
The Model 250 air brush has the advantage over spray cans in that you can mix your own colors, but that's really it's only advantage.
However, the Model 200 is a brush that will do 95%+ of all tasks you'll ever want from an airbrush. By the time you're ready to ask for that last 5% of capability, you'll be in a position to make an educated and experienced choice in a second airbrush.
The Badger Model 200 is also simple to use, easy to clean, durable, and if you do break or lose something (a tip or needle while cleaning, for example), spare parts are easy to find and relatively inexpensive (un-like many other airbrush brands).
Price alone might be critical for selection in your situation, but there are many ways to manage that cost, and there are also other important aspects that you should consider. By going this route, you can maybe spend a little more on a better quality airbrush without worrying about getting a compressor, but still be able to spray paint with a higher quality piece of equipment that will last and that you can maintain for the long run.
Good luck!