Anther thought, depending on your uses, would be to look at the 60 you originally were looking at, and if you only plan to do one or two basements a year, rent a larger machine, or an excavator to do those. I've thought about buying a skid myself for probably three (or more) years, but the work I do I seem to be able to do with the mini excavator I have, and my one ton dump. I rented a skid last year for 1/2 a day in total, this year, even though I did more excavating in general than last year, I still haven't needed a skid steer at all.
Three years ago the rental company and I were very good friends though, seemed like I had a skid out at least once a week for a day or so. It all seems to depend on the work that you have and are doing. In my case, I have enough truck and trailer that I can easily transport the skids that I need and rent, though timing can be an issue sometimes, it does keep the rental costs down.