So far, you are thinking exactly what i am thinking... $40 per hour/ $1200... I told the guy $40 per hour... Problem is he said "he only has about $700 to spend on the job"... I told him that he'll be very lucky if he can get it done for $700. I know that I wouldn't do it for that... He still wants me to come look at it and give an estimate and he's aware that I have a 38 hp tractor and a 5' Bush Hog.... I'd like to charge a flat rate... I definately need the job, but will not do it for $700. That's just crazy!
I would do that job for $900 and I'm considered on the expensive side around here. In rural areas he'll find someone to do it for $500 or so. (some farmer with no insurance, taxes, etc). Take me about 5 hours. I do this for a living. (that's not a typo BTW, 5 hours is a good number)
Unless it's something really custom, you'll find charging by the job is the better way to go. You'll also find that some things either require bigger equipment and you simply can't do them. You'll find some jobs that are perfect for your sized tractor. And you'll find some jobs are too small to be worth doing. (you need a minimum charge). And sometimes you find that your great idea isn't such a great idea and the area doesn't support the work.
It COSTS about $30/hour to run a compact sized tractor. maintenance, depreciation (you have to replace it sometime), tires, fuel, etc, etc, etc. You have to account for transportation time/truck/trailer/etc. You have to account for insurance (both liability and commercial vehicle), workman's comp (if required in your state), advertising, marketing, communication (cell phone), etc, etc, etc
someone in there you're supposed to get paid.
somewhere in there your supposed to make a profit.
I charge by the job, but I'm not getting out of bed for less than $90/$100 an hour. And I"m not making much of a killing, but at least I'm not working for free.
You'll find that ALL bushhogging jobs have crap out in the field, they don't call you til it's real tall and you'll never know what's out there. That's the business and that's why it's not free.