Team Foundation Server has a workgroup edition which works out much less expensive for small shops (up to 5 users). You don't even pay for it as a product in its own right - it's included in the VS Team Dev licence. I was told (by a Microsoft VAR) that the minimum setup is one VS Team Dev licence and the remaining four can be VS Pro plus Foundation Server CALs. The gotcha is the 5-user limit - more users and you will need the full product.