Fewer than most people build.
FOR A SMALL BUSINESS
Six to twelve pages covers most. Homepage, three or four service pages, about, contact, and any legal pages.
WHY FEWER IS BETTER
Every page needs writing, maintaining and updating Thin pages dilute the site rather than adding to it A visitor faced with thirty menu items finds nothing
WHEN MORE IS JUSTIFIED
A genuine page per service, where you offer several distinct ones Location pages, where you serve several areas and have something specific to say about each Products, in a shop Content, where you publish regularly
WHAT NOT TO CREATE
A page per keyword variation Pages duplicating each other with a word changed Pages created because a template had a slot
THE TEST
Does this page say something the others do not, and would someone search for it?
If not, merge it or leave it out.
GROWING LATER
Start with what you need. Adding a page later takes minutes; removing a site's worth of thin content takes considerably longer.