Playing in the street

Well, the title kind of says it all, I've been wanting to play in the street for ages, yet I don't know how to get a proper sound, some people tell me to buy an amp that works with batteries but the ones I've seen sound a bit crap, others tell me to buy an acoustic but I'm not up for expenses. I've seen people that play in the street and have a great sound even in youtube videos so there must be a way, right?