I had a title mma muay thai bag in my garage for years. It was on a century bag stand. I used rope to attach it in order to keep it off the ground. It was fantastic for punches, when you do the kicks you just have to make sure you are careful and be creative with your angles. I always tried to land the shin on the front of the bag. I can honestly say, I never kicked the metal.
I would definetly say it is worth it, if that is your only option. Most of them also have those speed bag platforms...which can certainly be used once you bolt them down...and get a better speed bag for it.
Sakuraba, Bas, Fedor, Igor
Tommy "The Hitman" Hearns