In reply to manicpb:
It's not usual but some companies are open to negotiation if you're willing to buy off them. They vary but I've seen it more like 25% up front, 50% to start installation and 25% when it's finished, depending on the size and scope of the wall this could take several months away. Obviously you'd have to phone as ask to arrange a meeting or something, I'm sure most would be glad to get 50% up front.
Regarding calculating the climbing area, most companies will offer a design service for you if you can provide them with a plan drawing of the building you're looking at using along with a brief of roughly what you're after. They can then provide you with 3D visuals of the the climbing wall from several angles and a detailed breakdown of surface areas and matting requirements etc as part of the quote.
I'm also a climbing wall designer who does work for some of the major companies so there is half a chance it'll be me doing that, depending which company you go to.