Most small business people (and this business you are looking at is a small business) have an incredibly inflated sense of what their business is worth. The posts here are all right on (although some are a bit more blunt than I would be). The fellow wants way too much. Wayyyy to much.
At the very least, you want to see 3 years Schedule C's to verify the dollars. And, I would also agree that his "profit" includes his salary, or draw, which must come out of the equation.
There is alot of work to be done in evaluating what you should pay for this business. And, in our industry, "fair market value" of mowing equipment is what it would go for at auction, not on a showroom floor. That lends me to believe that the equipment number put forth is also inflated.
I've bought numerous local small landscape and snow business, and for the volume you've put forth (including equipment), $50K would be a generous offer (with the limited information put forth here). And, make him finance it, with caveats for loss of customers down the road (like, next month).