Dig out a crawl space? Good investment?

[David Hayes]

Just curious if anyone has any experience digging out crawl spaces to make livable basement space?  I have a house in a nicer area of Cincinnati (Wyoming), I got it for $240k, houses nearby are selling in the upper $300's but have a little more space.  The only other major repair needed is the kitchen, other than that it's pretty basic stuff.  I'm curious if anyone has dug out a crawl space to add square feet to the house and if this is a good investment (could be added as square feet to the listing with a entry door to the basement also added).  Or is it better to do a room addition for more space?

For reference, my crawl space is already about 5ft deep, I would want to dig to have a normal ~ 8ft ceiling. It would add about 900 sq feet of space, and if I added a bedroom/bath, etc I could really improve the specs on the house. 

If you've done this before I would love to hear your experience.  If you have a contractor in Cincinnati area who does this I would definitely like their info.

Thanks!