By "lights" I assume you mean the fixture? A MH ballast is an MH ballast. The ones that run aquarium lights are no different than the ones in a yard light, for instance. The aquarium industry generally does more brisk business with the more efficient ballasts for several reasons:
1. They are more energy efficient. The reasons here are obvious.
2. The lamps generally last longer. Over a long enough period if time, the cost difference of the ballast pays off.
3. They run the bulbs cooler. Less heat in the water.
4. The ballast themselves are cooler. MH lights are designed to be run in large open areas. People generally don't want a ballast that heats their rooms.
5. They are quieter. No hum.
However, if you are trying to go cheaper, you can absolutely use any old MH fixture by either using it on it's own or gutting it an DYIing a fixture out of the parts.
The only thing you have to remember is that MH bulbs come in two flavors, Probe Start and Pulse Start and you have to get a ballast that matches. I can't remember which is more common, but if you use a SE (Single Ended) lamp, then just about any Lowes/HD/Cheapo fixture designed to run the same wattage bulb should light it.
Just don't mix wattages.
