The number of tomato plants will be relative to how well they produce in your area. Last year I planted 27 plants. I canned tomatoes until I didn't have shelf room to store any more, and then I froze some and dried some. Gave everyone in the neighborhood a lot of them, took a lot to the food pantry, and fed many to the chickens. At the end of the season, I still had many go to waste. This year I'm not going to can any as I will have plenty left, and I'm planning on only a few tomato plants for fresh eating. That will give me space for some other things. Sandy is right, you learn by doing, and then the next year you make adjustments. I've had gardens for most of my life, and I am still learning a lot. I think the best advice is to not over do it the first year. If it gets to be too much to manage, you can be discouraged. Good luck!