Tell your friend to either save up or consider getting himself a desktop from Walmart. A decent gaming rig will set you back around $500-700, depending on the parts that you get. Mind you that with that price range, the graphics will be good for a minimum of 2 years.
CPU chips change every year.
Motherboards change every half year (if that).
Memory changes every 2-3 years (why I love memory).
Video cards change every year.
When it comes to power supplies, just gotta find the right specs for a real good price. When it comes to shopping, it depends on where you guys are from. If you live here in USA, we highly recommend Newegg for their free shipping offers. In Canada, ive heard of a few sites including the Canadian version of Newegg. When it comes to overseas, other guys can chime in on that.
Overall, if your friend wants a great gaming machine on the cheap, just simply tell him to be patient & continue to save $$. Nothing is worse than setting yourself up for cheapness.