A) I would buy some iron on letters and plain t shirts a cheap nice way to make the shirts. You can buy the letters from this site:
I personally like the retro ones. Otherwise you can buy special printer paper that is iron on and print whatever to put on the tshirt.
B) here's the shirt for sale
C) what are the funny logo shirts for?
I think the best site is threadless.com but they're about $18 generally, I don't know if you consider that cheap. Keep an eye out though because often they do $10 sales, they just did one for Halloween, at the moment they have free shipping if you buy a hoody or Select product, but they're $35 plus.
Cheapest is 6dollarshirts.com but I think they're generally pretty lame.
Other good sites are snorg tees, busted tees and loiterink.