With 300-500 bucks you can get some nice equipment, man. People might crucify me for saying this, but my light reccomendation is a nice High-Output (HO) T5 Fluorescent fixture. I am saying this for a couple of reasons: 1.) Cost - The cost of a fluorescent fixture is nearly the same as a HPS/MH fixture, but costs much less to operate per month (My T5 is around 6-7 dollars per month). 2.) Heat - Fluorescents put off much less heat than the other options, which allow you to place your plants closer to the light while still not burning them (I've even heard of people putting a piece of plexi-glass on the fluorescent fixture so the branches can touch the light fixture - As to if this is a good idea or not, I'm not sure.) 3.) Security - Although it's very uncommon, IR flyovers are more likely to show a higher heat signature with hotter lights (duh, right?).
This looks like it could grow two nice big girls for you:
http://www.thehydrosource.com/Lighting/Fluorescent_Lighting/T5_Fixtures/Hydrofarm_T5_Fixtures/Hydrofarm_T5_4_Ft_4_Tube_Commercial_Fixture?zenid=mqmar651atav46qdce12oerjd6
As far as your dad's shop, don't bother looking for a light in there (unless your dad owns a lighting store). This is assuming you are going with fluorescents, as all lighting fixtures out for horticultural purposes are very high output. If you were to go buy a fluorescent lighting system for a workshop at Home Depot right now, I doubt they would carry T5 HO systems, more likely than not, just T8 and T12's. These lamps don't put out enough light (measured in lumens) to properly grow plants...unless you had a shit ton of them. Also, you probably won't be able to get a good soil from Home Depot, you might want to look around your area for a hydroponics store/garden center. Either way, do some more research on what all you will need to grow, how it's done, look into different online stores to get an idea of pricing, and figure out what you want to do.
