The fee in my community garden is $10.00/yr for a plots that range from about 6'x15' to 15'x25'. Hardly enough for anyone to make a profit, but then, my community garden is not a profit-making venture.

Don't know where you are in Michigan. I'm in the Ann Arbor area and community garden plots here measure 25'x30' and cost $90-$120. The program here has about 250 plots. If you are near an urban area that does not have a program like this available, you might be able to make some money, but it can be time consuming, too. Just running a community garden program is a lot of work.

$35 annual fee for 21' x 16' plot with no service other than monthly mowing of paths and city water via a standpipe at the garden entrance. Restrictions are 'organic only' which would protect your farmland.

What you can charge will depend on how far people need to travel and what you can offer. Probably, fencing, water and a port-a-potty or old fashioned out house would be a minimum to start.
Have you tried advertising? I think it will work if you are near a place with apartment dwellers or small yards. Good luck

Ours is $50/season (February-July and August-January) or $80/year for a 20x20 plot, with a $40 tool deposit the first year. Each gardener is also required to put in 6 hrs labor per season, with any shortage charged at $10/hour. Here, the fall garden is just as big a deal as the spring garden; where you are, I doubt the seasonal division would work.

The garden provides water, a small building housing offices and a restroom, lawn mowers, a pretty large-scale composting operation, and tools. They're pretty generous with the tools; I'd say there's a rake, a spade, a shovel, a turning fork, and a hoe for every 10 gardeners, plus random numbers of post drivers, scythes, etc. Oh, and a dozen wheelbarrows or so.

I don't mean to be discouraging, but frankly I doubt that you can make much profit this way. Our garden has some support from a non-profit agency and also has a big plant sale fund-raiser every year, but we're still always hurting financially. The rental fees basically cover the water bill and not much else. We're on unused state-owned land that's leased to us for something like $1/year, so we don't have mortgage and tax payments, which I'd guess are your #1 expense. A garden rental operation might help you with some of the expenses, but it's not likely to generate income. And if it's just you, the landowner, opening up space for people to come garden, you're going to have a HUGE insurance liability. I mean COLOSSAL. Don't even think about starting something like this until you've consulted at least one very good lawyer, because otherwise one cut finger could wipe you out.

Have you considered joining forces with a non-profit like a school, a church, 4-H clubs, etc? You let them use the land, they take care of all the administrative hassle and take on the liability, and you get a tax break. I don't know what land values and property taxes are like where you are, but down here, getting out from under the land tax would put you farther ahead than a small rental income would. You'd get the tax break whether the plots were all rented out or not, and you wouldn't have the advertising costs, etc.

Why don't you talk to your county Extension advisor about the idea? S/he would probably have a good sense for whether or not it's a feasible plan, and might have other good ideas that we'll never come up with here. And talk to an accountant and/or a lawyer very early in the decision-making process.