Everyone has given good advice so far. I will highlight a couple and make a couple others.
As stated, if this is an established company that already has something established, it's difficult to imagine they have zero funds to pay for a website. Most of the time these "deals" are proposed when someone wants to start a business and are just starting up on their own savings. If they are running a business already, they know how to manage funds for expansion. Any business would like to find a cheaper way to get things done, but that doesn't mean you have to accept (not fully at least).
One thing you have to think about is that you are essentially opening a new business location for them. Just like if they were to open another store in another city / state, you are opening a store online for them. You are "stocking" the store by adding all of their products, you are preparing the look and checkout process for the store and (by the sounds of it) you will probably be in charge of keeping the store open and updated. Is this correct? If so, you have a much higher stake in the company than simply taking 5% of the profit they make on orders (or whatever they would offer you).
Personally I would not work for 100% profit. You are doing all of the work for that part of the business. I have set up ecommerce websites for businesses but because they did not want to spend the money to have me populate the website. So instead I set up the CMS / Data Management and gave them access and told them how to do it themselves. 60 hours of photo manipulation is a huge amount, and based on that number, I'd assume the product entry would be significant as well. A lot of extra work that could be handled by someone in-house I think. If you are interested in becoming part of the business, I would at least ask for a portion to be paid up front and then a percentage of orders after that. The problem here is that if you are not a partner, you will not be privy to essential information (like how much is actually profit vs what they tell you) and also you have no say in how the business is run. Your share is dependent on spending for advertising, costs associated with the website, etc. If you have no say, you are at their mercy and will probably not see much in return. I may be wrong, but there have been more bad experiences with this type of situation than good ones.
Whichever method you choose, the important thing to do is to price out the work you would be doing no matter what. You should price out what it would cost 100% and make note of that cost. Whether you charge them that amount or a portion, you need to factor that in to how much you should be compensated for ... if not more down the road for helping expand the business.
It's really a personal choice you have to decide for yourself. Only way to learn is to try what you think you'll be comfortable with and go for it. It may be a great experience ... could be the worst decision you'll ever make. But at least you'll learn something in whichever you decide! Good luck!