Your research prospectus should answer all of these questions, in order with highly detailed answers. His field is business, HIS MAJOR IS INTERIOR DESIGN

What argument in your field are you interested in researching and writing your Researched Position Paper on for this course?
Why is this argument important in your field?  
What are a few different positions on this argument?
What is your position and why?  
How did your position develop?
What might you accomplish by joining this argument in your field?
What could you look for in your research to help you make your argument stronger?
Is this issue still significant or is it becoming outdated and how do you know?
How will your paper add to the argument about your topic?
What might an educated audience of experienced professionals in my field know about this argument already?  

After you’ve considered all of these questions, make sure you didn’t make the overwhelmingly common mistake of choosing a non-argument argument or a non-position position.  For example, pretend you are going into social work and you think you want to write about child abuse.  You end up stating something completely obvious like, “Child abuse is bad.”  That is a “d’uh” statement to people in your field (and outside your field as well).  There likely will be absolutely no academic research stating that child abuse is good.  As such, there is no argument here.  There is no other position in your field debating against, “Child abuse is bad.”  This is not an argument piece; it’s an obvious piece and doesn’t fulfill the course expectations.  
Instead of non-position topics, consider a topic that is open for debate.  For example, in my field of teaching people debate the merit of extra credit.  There are professionals in my field who are for extra credit and those who are against it.  It’s debatable.  There are arguments to be made.  There isn’t a clear right and wrong.  If I were writing this paper, I could choose extra credit and begin to share my position within the argument.  
My advice is this:  Choose something open for debate, not something that is obvious and without argument.  Then, work through the prospectus questions above to help you frame your thinking.