Ebay, guys, Ebay. Used minis -- painted or not -- are cheap there. I go there first. I picked up 3 squads of eldar aspect warriors that are quite nicely painted for only 200% or so of what the models themselves cost. Considering the time it saved me painting 18 models (I average 5-6 hours on one space marine, I'd say), I was quite happy. It'll be 6 years or more before I finish my marines and get around to painting all my Eldar, and I'd like to field painted units in the meantime.
But, crappy painted models or unpainted models can be bought for a song. And, if you can find ugly painted ones, buy them for cheap and repaint them. Soaking metal minis in acetone or plastic minis in a Dishwashing Liquid mixture removes the paint (you'll need to scrub with a toothbrush, of course). I picked up a horribly painted razorback, ripped it apart, got the paint off of the parts (enough to repaint anyway), then beat it up even more with my modeling knives to show combat wear. It's a way cool model that looks like it truly has seen a millenium of battle.
