Should I finish my MBA and wait until I have money to invest, or should I start real small to get a business going sooner rather than later?
The biggest challenge for business owners day-to-day is simply learning what it takes to run a business profitably on a day-to-day basis. Home-based means you can save on overhead, keep your expenses in line and have some cushion for your mistakes--which you inevitably will make.
Running a home-based business will also allow you to apply your MBA to the basics of running a business--skills you will need when you "ladder up" to your dream business.
This means learning all you can about buying with no money down, learning about vendor finance, never paying retail and learning how to create--or what I call "buying"--customers.
I would also say, don't rule out a network marketing business. They are low-cost to start and will teach you all about sales and building a customer base--two skills you will need no matter what business you decide to pursue.
All the best.