Wish things were as simple now as they were in my day. There was only one choice in CT back then: a walk behind Locke. If you wanted to ride, you could put a sulky behind it. You could read a newspaper and steer with your feet if you had enough open space. Those machines lasted 40 years for many people and the 75 inch machine could probably fit through the 42 inch gate with the gangs all the way up. The 70 incher certainly would have. I think they still make them, but from what I've heard the quality went out the window in the 70's some time. Today's mowers could never, ever manicure a lawn like those gang reel mowers did. And, at 75 inches, you could cover a lot of ground at a very comfortable walking speed. Of course they were bears to maintain - you couldn't sharpen them yourself without a shop full of tools, and if you hit a rock, you could be in big trouble. Those were the days when cutting grass was a pleasant job.
From what I've seen, the Cub Cadet mowers are pretty much light duty stuff designed for the consumer market. I'd look to the well known pro machines for a business - Kubota, Scagg, Yazoo/Kees maybe Ferris if they make 'em, etc. That 42 inch gate really cuts into your profit potential - as someone else mentioned above, I'd consider replacing the gate before buying a machine. If you want to save money, I'd go with a commercial walk behind first and when your profits permit, maybe upgrade to a commercial quality rider.