Automated Sales Form / Email for Wordpress

Hi, I need someone to create me with an opt-in form that integrates into Wordpress, preferably in PHP. It will be a sign-up / registration form on my house selling website, that analyses the price point given by the user, and collects it, and then makes an offer based on the price point they provide. For example: 1. User goes to my website, fills out the form. They say that their product is worth $100,000. 2. The script records this price and their information they enter into this form. 3. The "offer" that is made by the website for this product, needs to be based on the price they enter into step 2. I need to be able to control the amount on offer - so let's say I want to offer 10% below the price, this should be controllable and be a site-wide setting. Therefore I would need to be able to specify "-10%" somewhere. 4. The script will then calculate the new price with 10% reduction, and display it to the user saying "We will offer you $90,000". 5. Finally I'd like a basic newsletter system - can be based on a current Wordpress plugin - that emails the user on the email address they gave, the offer they were offered. So basically a reminder every few days that their offer is still valid. The website will be a house valuation service whereby visitors will enter their house price value and our software will calculate 10% off and make an offer to buy it at that price. You can use a WP Plugin for this project.