Agree with all that is said above. I had never airbrushed before painting my Fett. I purchased an inexpensive dual action from Princess Auto (I believe similar to Harbor Freight in the US), it turns out its a repackaged Beaver B200. Not high end by any means, however with some practice I was able to learn to use it relatively well, how viscosity of the paint and air pressure can have dramatic differences on how the paint comes out of the nozzle. Proper cleaning between colour applications and when you are finished using the brush will impact its usability as well as longevity.
Now having used an inexpensive brush and learning some of the in's and out's of airbrushing I am contemplating moving up to the next step, an Iwata is in my future, simply because airbrushing is quite fun!
So start with an inexpensive option, play around, practice lots, make sure it's clean and above all enjoy what you do and you will have airbrushing licked in no time!