Why not try a google search on Dr Bud GreenGenes. He's doing a compact perpetual SOG (sea of green), all CFL bulbs. It might be right up your alley--small, continuous, lots of plants. so you may not have to wait for a plant to grow 3-4 feet, hoping for a solid yield and then waiting an entire grow cycle for your next plant, when you can grow lots of smaller plants, keeping the duration between harvests down. Your harvests will yield less, but more frequently.
I'm trying to dial my setup in right now, most of my plants, however, don't get beyond 24" high, but i keep a cycle of clones. I'm looking at a total of about 18 plants in various stages of veg and flower.
Once you get used to cloning, (and research it well), you'll be able to dial in your grow fairly well. It'll take time, i'm at about 6 months old now, and i'm still fucking up all kinds of ways (mostly with my soil). But truth be told (at least in my experience, thus far), cloning isn't hard, it just requires a bit of patience and learning your plant(s).
I'd KILL for 3x3 space. i have 2lx2wx7h, and in it i'm running my clones (as
@bigsteve mentioned), my flowering and veg chambers.
The
Key Takeaways i've learned thus far in flowering is the dangers of light pollution. I had a thunderbud plant come up with a strawberry cough and a sage/sour. and because i have only one door to the entire cab, the light pollution affected, and hermie'd my thunderbud. So in whatever space you build, I would suggest keeping light segmentation in mind.
Also, your soil/growing medium. Think about how you want to deal with this. Soil is easier in some respects, hydro in others. do a little reading on the merits of each, and then settle with something that works for you.
Lastly, Light choice. I think, with the space, you might be able to get away with just using CFL's. But if you're looking for high yields, you might want to consider a 150 or 300 HPS (at least that's what i've read. i'm still in the CFL game, i love it, and my electrical bills are low as hell--I have about 345 watts worth of total lighting in all three chambers--all 23 watt cfls), though cfl's may work. I'm no expert here, but if you're looking at cost factors, my lighting system cost me 50 bucks: wires, sockets and wood to tie them down to. while my bulbs, well, they're 4 bucks per 4 pack at a big lots or home depot, 100w equivalent.
I hope this helps a bit. I'm still new, but i know how overwhelming the starting up process can feel.
Best wishes, and not just for your grow!