You can, it should be noted,
play the game without spending a cent, using V40K. It's not the same as using actual models, sure, but it works almost as well. You can find the vassal module by searching for "vassal" on 4chan's /rs/ board. That also lets you play with people who are literally on the other side of the world. I've done so a few times, though their Lolstralian internet tends to give out.
I would highly reccomend not starting with the Eldar, as they are basically the "Elite Race", you need a really solid understanding of the game to get anywhere with Eldar.
If you want an army that uses small numbers of high-point units, you're choices are basically Space Marines and Toasters, possibly Chaos Marines.
I don't know, Loldar require some thought, but they're not
that hard to use to hilarious effect. Their good units are absurdly expensive though, both in points and IRL jewgolds. The 500 point jetbike army I used and loved would cost around $200 to buy. For about a dozen models. >:|
-What's a good army? I've played Space Marines once before. I was thinking Squats Eldar, maybe. They're long range guys, right? I'd also like an army that's effective with fewer, high-point units than the other way around, mostly for price reasons.
Eldar are fairly short range, but fast as fuck all and devastating once in range. Tau and IG are more long range oriented.
-Is there a way to get models without paying a billion, million dollars?
Rob a game/hobby shop?
You might get some cheap buying used models, though if they're going cheap they're probably poorly put together/painted or broken, I seem to remember hearing well done shit sells for more than new. Don't have any firsthand knowledge of this though.
-Can I play Squats even though they aren't in the game? Do you usually just collect one army, or do you like to spread the love? Do people ever do mixed-army fights?
From what I understand, any Imperial units can be tacked together into an army (guardsmen providing cannon fodder for marines; guardsmen providing cannon fodder for witchhunters... you get the picture). I also hear Tau can appropriate IG units as local auxiliaries. Don't know how true either of those rules are though.
Anyone else think it would be hilarious to build a model out of paint and one of those cheap little plastic soldiers (as in, very thick paint, layered on until it was the shape of whatever), and take pictures showing the steps, with the comment "I forgot to thin my paints D:"? :3