I'm a currently a college student earning a degree in Computer Engineering, so in terms of business, I have no idea what I'm doing. I've asked to create an ecommerce website from scratch.

Here are the things I've decided to do for them: ( If you think I'm missing something please let me know )
1. CMS: Magento
2. Theming ( I'm doing this from scratch so no pre-made themes for me )
3. Product Image enhancement ( they have pictures of products, but they need to be photo enhanced ). At least 60 hours worth
4. I have to input all of the products ( pics, info, etc... ) There's a lot of products!
5. Possibly do a little SEO ( which I'm not really familiar with )

He's become somewhat of a friend of mine so I don't want him to rip his arm and leg off to pay for it. We've vaguely verbally agreed to me receiving a percentage of the profit from all of the orders from the website. I just don't know what percentage is fair or if I should even agree to a percentage type of compensation. I'm not a business partner. This is a manufacturing business already established in LA. They just need a website for dealers and online customers.

I've already read the sticky above and I've already read some of the sitepoint products pertaining this topic, but I'm still unsure of what to charge.