Thanks for all the advice. I went into Excel and tried to create a rough bottom line. Calculated average fuel costs per hour, a small maintenance fee per hour, etc. I came up with $10 bottom line just in fuel costs per hour which could change according to fuel prices.
I came to the conclusion that I would need to bid no less than $35 an hour for 20 mowings, bringing the bid up to no less than $22,000. So I definitely think me winning the contract is out of the question.