Gazelle - Horrendous running costs
MD500 - Supposed to be great to fly but not much room in the back - depends how often you're taking passengers.
I would go for an R44 Raven II or a Jet Ranger. Although a nice Jet Ranger ain't gonna be cheap.
Maybe get an older R44 Astro/Raven I if you budget is limited.
I think an R44 would be a better bet to lease back to a flying school.
Or if you're £loaded, how about a Single Squirrel? (AS350)