New to longboarding. Is there anywhere I could get a good longboard for a good price?

I'm wanting to get into longboarding, so I can cruise around with friends and have fun, but all I have at the moment is an old skateboard from my brother. Where can I get a good longboard for a good price? I don't have much money, being a 16 year old that can only get money from a few chores around the house. It could be anywhere from free to cheap, as long as it works well enough I'll be happy!

Thanks!!