Need help, researching starting a kitchen design business

[Trey Whitlock]

The people we hope to have as clients are probably using bigger pockets and if this isn't allowed I'm sure someone will let me know.

My wife and I are laying ground work to start a kitchen design company around February.  She currently works at a big box store and has been the head kitchen designer there for a couple of years.  She doesn't like the direction things are going so we're doing the research to see how feasible it is.  The plan right now is for her buy the software and start doing designs as a second job.  If things look good, eventually we'll transition to full time.  

We've always wanted to start buying real estate and building a portfolio but we've never been in a good enough financial position to do it.  We're hoping this might give us the means to head in that direction.

Here's our problem, she doesn't know what to charge for a design.  We don't even know where to begin trying to figure that out.  I'm sure many of you know that big box stores do free design if you buy the cabinets and installation there. But what does just a designer charge?  Any help is greatly appreciated.