I agree with Kurt. If you want to work for a major corporation with little chance of becoming one of the top few, I would look at the MBA program.
However, if you like lawncare, are making a decent living, and like having a good deal of control over your situation, I don't think the MBA makes a lot of financial sense. I don't think any of your lawn care customers will care whether you have an MBA in business, or just an undergraduate degree in advanced basketweaving, or for that matter any degree at all. As long as you provide good service at a fair price your customers will be happy.
That being said, picking up business courses from whatever source is a good idea to help you in your business. I just don't think the MBA would be worth it.