You can easily bypass rattle can, which are nothing more than badly designed airbrushes if you think about it.
Not knowing your location makes it difficult to advise on airbrushes, but Dixie Art
is a good place to buy from and I can recommend the Badger 100LG ($72
delivered in the US) and their 105 Patriot ($73.50 delivered). Iwata
and Paasche also make brushes in the same price point.
I recommend gravity fed airbrushes, as they are slightly easier to clean, and allow for greater control for fine lines.
You'll spend more on a compressor than an airbrush, $120 - $200 is
a good price range. If you can handle the noise, garage style
compressors also work, and are multi-taskers. I use one with a 3 gallon
tank (which I wish was larger) and pipe the air into my man cave.
You'll need a pressure regulator and a good moisture trap as well, and the price range I quoted above should include both.
Every bit as important is a spray booth and respirator. Paints are fairly hazardous materials, and if you have children around, it is especially important to contain the hazards and vent it properly. At the very least, breathing in teeny-tiny bits of dried paint is not recommended. Expect to spend $200 and up for a good booth. You can build one yourself, and there are many threads about that if you search for them. I have a homemade booth and I can attest to both the ease of construction and the difficulty of proper design. I've spent around $150 building the booth, and find that it is less than perfect. I expect to rebuild it this spring and I'll probably end up spending as much money as if I just went and bought a top end booth!
You CAN live without a booth, but only if you use a respirator and have no-one else around that can breathe in the fumes and particles. Spray booths also help contain the odors associated with painting, which can be important for maintaining a happy home!
There are many modelers who choose to use a brush instead of an airbrush, but they are fairly rare and must have the patience of Job. There are a few on board who stick with their brushes, for whatever reason, and do a fantastic job. I'm a MUCH better painter with an airbrush in hand!