“The Next Step” would be something to tell your customer how to actually accept the quote. It might be a signature line at the bottom with instructions to fax the document back over to you, or even include a place for them to enter the credit card # for the ‘down payment’.

Also, you can mention more payment method options such as leasing, terms, etc.

There are obviously innumerable ways to accomplish all this (you could even have a separate document to handle the items I mentioned that contained a timeline, and deliverables, etc) but I think at the very least a “Next Step” direction at the bottom satisfies the call to action.