How big of a plane do you envision building in the future? That's a key to what you should buy as far as compressors go. For R/C, and anything from a .40 size up, an air brush really has very limited use. What you should be looking at are small automotive type touch-up guns for adequate paint volume. You can actually get some relatively cheap touch-up guns at Harbor Freight. Tower Hobbies sells a pretty nice little gun by Hobbico for about $50, see the following link. I have one and it looks in the picture to be some type of cheap plastic but it's actually metal.

http://www3.towerhobbies.com/cgi-bin...&I=LXHEY0&P=SM

Also check these especially the last one. The first one is like the Badger 400 style siphon type touch up gun...the price is amazing. The last one is a starter set.

http://www.harborfreight.com/cpi/cta...?itemnumber=86

http://www.harborfreight.com/cpi/cta...emnumber=94572

Enjoy...