need some advice

Hi,
I am learning PHP and mysql. I have got some offer for an e-shop. Actually this is my first business project.
I am working with some guy who owns a company, but is doing only simple HTML pages. He has got a client who needs e-shop.
I have already started with building the application, but I have a feeling that this guy who owns a company doesn't have good intensions. He sad we would share the profit fifty fifty, but he doesn't want me to speak directly with the client and I don't know what are the prices for this kind of applications.
I am not even sure if sharing the profit fifty fifty in this case is fair. He has already done the design and HTML page for this client and got payed and now I will put in the same page some PHP so he will earn twice.
I will do this project to get some references, but I don't think it is right to work with this kind of people.
Any advices about the price or opinions would be helpful.