Xbox Live purchses

I'm a n00b to the 360

If I purchase content over live on a friends console via my account, will I be able to re-download the same content I purchased to my home machine without additional charges?

tl;dr

Is purchased content a per machine setup
or per user account?

Per machine I believe.

Yes. You can download anything you've purchased anytime you want to any machine you want.

There's a catch, The stuff you download can only be access if you're Logged onto your account OR if it's downloaded to the machine you first downloaded for it.

So anyone can play your arcade game for free if they use your xbox, but if you brought your gamertag to your friends, he can only play it if you're logged on too.

you BUY stuff from XBL ?