Several questions about hair extensions, stylists please help?

I think they can cost from a few hundred to a thousand dollars, so you might want to shop around. Hair extensions will damage your hair, they will put stress on the hairs they are attached to, sometimes causing them to snap off. When you take them out your hair will be shorter than it was before. How often they need to be re-tightened depends on the technique used to bond/braid them into your hair.