Your only limitation will be your ability to produce continuous fruits...
Hidden expenses...
- Time (How much is your time worth an hour?)
- Water (Not a major cost.)
- Cooling (Fans, AC-optional)
- Heating (Depends on climate.)
- Light (250w is more than enough for personal use. That is 84Kwh a month.)
- - 250wh x 12 hours = 3Kwh, 3Kwh x 28 days = 84Kwh, 84Kwh x 3 months = 252Kwh.
- Start-up supplies ($300 - $3000, depending on your setup.)
Ultimately, you need to look into the laws. Some places don't allow "in home" growing of anything, due to fire and health issues. This will impact your ability to secure your grow and limit your ability to operate without drawing attention to yourself. (Bad guys in the neighborhoods are more of a concern than the law. Once word gets-out that you have a mini-grow-op... expect that your shed will get raided by men with guns, or teenagers.)
Play safe, and think about every aspect.
You can expect to produce that same quality of green for 1/10 the price, if you do everything right. Expect to save only half, if you do many things wrong. It is all a loss, if you do everything wrong!
Grow vertical, it is cheaper, consumes less space, yields more, and will destroy less if you mess-up. (Check my signature for a quick vertical calculator.)