Well, I feel for you. I think you are right on the edge. If you are handy with tools, I think you should probably do it. I have twice your size and I am happy to have my tiller, but it takes up a lot of space. Of course all my other useful stuff takes up far more space, and I am sometimes happy to have that too. Anyway, yes, I only use the tiller once or twice a year.

You could probably store the tiller outside under tarps or something. You might consider looking for a neighbor who might loan you a tiller for a price or for some assistance.

I've had a tiller for many years and wouldn't be without it. I mostly use it spring and fall to maintain four 100 sq ft vegetable beds. (I mulch with grass clippings all summer and pile on mowed-up leaves in the fall, so the soil is unbelievably rich.) I also use it, sometimes with the outer tines removed, to dig small flower beds before annuals are planted. I'd never rent one for all of this (too many small jobs to make it cost-effective) and I'm too old to hand-dig it all. lol

My first machine was a used Ariens. Inexpensive and a real workhorse, but done in by frame failure. I replaced it maybe 20 years ago with a Honda F401. I love Honda power equipment -- expensive, but well built with great engines. My '401 has reverse gear, which I love but they eliminated later, no doubt due to liability concerns. It's a center-tine tiller, mid-size, and folds to a very small size for storage.

Buy a used tiller, use it for a few years and then figure out where to go from there. Don't buy something cheap and poorly built -- it'll only frustrate you and won't be a good test of its utility. I've never owned a big, rear tine tiller, but I love the flexibility of my mid-size. If you buy a good tiller and don't trash it, then decide you don't want to keep it, you'll be able to resell it at a net cost way, way lower than what you would have paid in rentals.