Home Gardening (for profit): What's the best bang for the buck?

These last three years, I've taken to gardening in a big way. We're lucky enough to be renting from a fellow hippie, and this summer we had 4 joyous months of a supplemented grocery bill. I've been looking at a lot of different setups, techniques, and methods to maximizes long term profitability; companion plantings, succession plantings, mulches, organic ferts., compost, greenhouses, etc.

I recently saw a video of greenhouses which use a combination of hydroponics (in various layers through the greenhouse) and aquaponics. The yields they claim to produce are insane and I want a piece! But, what gives you the most bang for your buck?

I hear tell there's a certain Tree who's resiny buds fetch quite a price, but (criminality aside for the moment), does this produce generate the maximum income? Give the same resources, are Trees still your best bet for $$$, or is there something else out there which is more profitable? (ie. "cheaper sell price, but higher yields per plant/acre" or "less labour involved, but longer grow season" or "lower price, but higher volume or sales" or some combination of all these factors)

TL:DR -- What plants/methods yield the highest possible profit for the grower?