Lowryders are a great way to start. They are easy to grow, don't get too tall, and they an autoflowering strain, so they'll even grow, and flower, under 24hr lighting.

LowRdr's don't get any taller than 1.5ft in height, so for 6 of them, when the time comes, you'll need at least 6 3gallon pots for your plants to grow in, so I'm guessing...no more than a 4ft x 4ft space, and the height doesn't have to be any taller than 3ft.

Good choice on the strain. It was the second kind I grew and I was happy. Not huge yeilders, but it provided me with what I needed and I saved hundreds of dollars per year.