No HPS will screw into a regular socket, you need a special fixture and a ballast. You're looking at at least about $100-120 for a startup 250-400watt hps setup. Check out htgsupply.com
If you have to keep the HPS down due to heat and space you will get a small plant, this is one possibility, but this about as cheap as you're going to get going with a small HPS.
It's 70W of HPS.
There are other options abailable with these small HPS lights - I found this doing a search at Ace Hardware.