Just like kim said, it's all about the personality. There's a bunch of girls that like me, and hell, i only have 1 pair of shoes, 5 pairs of pants, and 6 shirts. so i wear the same thing every week, but in different combinations.
So all you have to do is get more 'game' than him. Just try to be nice, and dont go straight for the girl. Even if want her the whole time, you will just have to wait. Getting 'game' is all about patience. And if you just listen to a girl, or pretend to listen to them, talk to them, you will find out what they like. Then you can act like her 'dream guy', and she would eventually like you. And if you do it with too many people, you're S.o.L. once you find a girl you actually like, so be careful, foo.
And if you actually like a girl, she should like you for you, and not for who you are for her. So if you just want a girl just to have a girl, then do what i told you. But if you want a girl cause you like her, she should like you for you.
There are few places when you can sell without renting property or a market stall. If you were thinking of selling in the street you would need a street vendors licence from the council. If you are selling from home you should register your home address as a business address and pay council tax as a business rather than on residential property.
I couldn't see any problem with selling shirts with non-copyrighted sayings but you could have trouble with trading standards if the T-shirts are not good quality or if your printing doesn't last.