Creating a wizard marketplace

[Beth]

Since we are establishing that so many members have some connection 
to education, I'm hoping someone could point me in the right 
direction. :o)

I will soon (next month!) be teaching a class on Harry Potter at 
a "kids on campus" program. I remember doing an activity in junior 
high in which we visited other students' "businesses" and bought 
goods or services from them. I thought it would be fun for my 
students to create a wizarding world business and do this activity, 
but I'd like some guidance as to how to set it up logistically. I 
can't seem to come up with the right keywords for a search engine. 
Can anyone direct me to a website with a lesson plan like this?

Thanks!
Beth