For me growing vegetables isn't about saving money. Its about the accomplishment and doing something a little closer to nature. Plus I like the local flavor, which you can't get at the grocery.
That said give your radishes a try. I would worry about them bolting due to you indoor temperatures and lack of light. If those are problems try to find a variety that is "slow to bolt" and/or add a grow light.
Other things to try indoors are basil, microgreens of all sorts, pea greens, arugula, lettuces and scallions.
Good luck!
