Newbie help! Bulding Classes?

[Tom Port]

Hey everyone! 

As some of you may have seen in my introduction post I am new to the US therefore, new to some of the terminology used here. I am trying to get my head round building classes I.e A,B and C. 

What is the difference between these three in real terms? As a first time investor what should I be avoiding C's? I can google to get a generic answer but I'd love to get some "Live" Opinions. 

Also; I hate to ask such basic questions however, I can't find the search feature! If someone could point that to me it would be great. 

Cheers!