im sure you will come out ok your yield may be a little low on your first grow but even if you sell the excess at less than market value it should cover all of your cost of growing and eventually within a year probably the cost of equipment also.
the average person that is just growing what they need maybe slightly more and that does not need to rent a spot to grow can usually save alot over buying, but when you spend 7200 a year in rent alone plus add in your additional cost you will need to sell quite abit to cover the cost.