For a good starter light, any 250 watt HPS will produce pretty good results. Hydrofarm makes a really simple integrated ballast for like $250 new. I found mine used for $75. As long as you have ample airflow heat shouldn't be that much of a concern.

But if your thinking of getting a 250, then as long as you can move the heat along, why not just get a 400? You can produce a good 6 healthy sized plants under a 400. I say Metal Halide is a complete waste of money unless you find an amazing deal on a switchable, and even then why? After youve seen people continuously harvest INSANE bud with straight HPS and get the prety much same results with MH...