I'd be delighted to work with you getting the kind of information to invest in Columbia real estate. I work with several investors who have long term plans (like buying one or two properties a year to build a portfolio).
Please contact me for custom spreadsheets in the segments of the market in which you are interested. The statistics will be different depending on whether you're looking at single family homes, duplexes, condos, apartment housing, commercial properties and the price points involved. From your inquiry it looks like you're thinking about single family homes. There is a lot of churn in the lower end (which would be parents buying for their students) and the statistics vary a lot by part of town.
I can be reached at the following numbers, by email and through my web site.
Broker/Realtor REMAX Boone Realty
ABR, GRI, CRS, CFS, CNHS, e-Pro