Electrical Schematic Design

Rights to a product and proper compensation?
I recently joined up with a successful business owner who needed help with a product he was developing. This person understands electronics as a hobbiest, but is not an engineer. I am a senior in an electrical engineering program and had the know how and designed and built the additional circuitry that he needed.
Now the problem is, I could hand him the prototype I built along with the Schematics and he could give me X amount of money and be done with it. However, I have never done anything like this before and would hate to cut myself short. Would I have the right to receive royalties or commission on the sales of this product if it makes it that far?
Any comments or suggestions would be greatly appreciated. Thanks in advance.
You should have clarified this at the start of your employment.
If the circuitry is truly novel and not already in use elsewhere and solves a problem that has existed for some time, you might apply for a patent, but it is an expensive and lengthy process (tens of thousands of dollars and many years).
I would consider what you did an excellent addition to your resume. In the future, you should probably look hard at the patent agreement that you may be asked to sign if you opt for full time employment almost anywhere.
How to Build Electronic Circuits : How Current is Determined by the Electronic Circuit