How old do you have to be to have a book published?

Thats eazy fellow dude!! u have to be around 17 to do it. i think

to answer your first question, you can have a book published at any age. look up the internet for publishers, most reputable ones will have sites. You can submit manuscripts to most big publishing companies, but be patient.
Sometimes it helps to get published for free in a magazine or newspaper so that you can get feedback on how your writing is going. Good luck

you can be about any age to publish a book
you should probably do some research

any age
writer market