Im just returning to modeling after a LONG break, & didnt even know there was such a thing as airbrushes before I took the break.
Anyhow, as well as starting a kit stash & getting some tools together, one of my priorities is getting an airbrush - not knowing jack about them & being a sado, I have done quite a bit of research, general opinions seem to go like;
Gravity fed is most suited to airbrushing, don't go for any plastic bodied brushes, use acrylic paint (for starters anyway), dont go for anything that uses propellant cans.
Have a look at www.airbrush-pro.co.uk for some affordable & apparently reasonable quality airbrushes & compressors, £80 seems to get a reasonable start. On the subject of compressors, if noise is an issue for you, you could consider using a co2 bottle - you can get a bottle & required regualator for about £40 if you local gas supplier is kind enough to wave the cylinder rental.
I'm sure that there are others here who can advise with plenty of experience behind them, but above is what I have learned so far.