Need info on purchasing an airbrush!

Badger and Paasche are the old standbys. They are solidly built, easy to clean, and you can get parts. The hoses use standard fittings. Iwata has a very good reputation as well. They are more expensive and my impression is that the difference is mostly appreciated by airbrush artists. 

I would avoid anything from Testors/Aztek like the plague. I have a higher-end Aztek airbrush with interchangeable tips. It is very difficult to keep clean. The hose is a cheap piece of plastic junk and it uses a non-standard fitting so it isn't interchangeable with Paasche, etc. 

Be sure to get a compressor with a tank - you'll be glad you did. Also, an oil-free compressor saves you worrying about needing an oil trap. You still want a moisture trap, but oil-free gives you one less thing to worry about. 

I have a Paash, been using it for almost 30 years ad have put everything from laquear to Emron with no problems.

SIngle action means one control that handles the paint and air together.  Double action means you can control the flow of paint and air independently.  This allows more/fine control but also makes for a more complex device and probably a steeper learning curve.  The other main classification for air brushes is internal mix vrs external.  I would stay away from the external mix.  

The Badger 150 is a good brush to start out with but has the ability to do more as you learn to use it.  I own a higher end Aztec and I love the unit but it's not for everyone.  I use mostly acrylic paints and I keep a 5 gallon pail handy to clean the unit.   I just remove the paint cup and run the unit while it's submerged and clean it out.  All airbrushes require scrupulous cleaning or they will not work properly.

I use a Passache VL series. A friend does pro paint with the H series. I have had this gun for many years and it is reliable and easy to clean. The VL is a internal mix two stage unit, press the trigger down for air and pull it back slowly for paint. The farther back you pull it the more paint you will spray.There are interchangable tips/needles for different types of paint.  You can also get a cloth covered hose in several lengths. I use a compressor that I picked up at my local hardware store for $99. It has a tank, pressure regulator,and auto cutoff. It is small ,compact and fairly quiet running. I believe it is made by Senco or something like that.

Frank