Shop space with living quarters... anyone have any thoughts?

[Rusty Thompson]

I've pretty much focused on SFR so far & I have zero experience with commercial property. But the other day I was on my way to one of my properties a transmission repair shop I pass all the time is up for sale. I instantly had the arbitrary thought all investors experience... hmmm I wonder how much they want for that. But never thought to look into it.
Well a couple days later I was doing some market research and stumbled across it on the MLS. Besides having shop space, it also has a attached 3/1 dwelling. Now that sparked my interest. I did a quick walk through & its very "run down" on the inside.
The problem is, I don't know how to value it. Comps are going to be impossible to find. Does anyone have experience with this kind of property? How much over market rent should I expect since they are getting business space & living space? Would it be best to rent them individually, then offer a discount for both? Its def. a niche market.

MLS listing
http://www.wvmls.com/property_single.asp?ID=641463
I feel its still over priced

shop space for rent
http://salem.craigslist.org/off/2634480712.html

any thoughts appreciated