Quote Estimator / Payment Button

So, I need to build a new site for a client who needs a way to generate a quote for a prospective customer, automatically email them this quote, and include a link (probably Paypal) which would have the customer make a deposit payment. The client is in the landscaping business. Many of the items on the quote could be standardized on a form but they need to be able to add ad hoc items on the quote and the costs. They also need to be able to specify the amount of the deposit required in some way.

Do you know of a good way to approach this challenge?

Thank you