Yeah you guess the man hours and then bid but if your not familiar with bidding leaf clean ups be prepared to screw up.
The first clean up I did I told the guy $300. After about 16 man hours I was steaming but happy to just be done. The guy gave me a extra $100 but I still did the job for half price.
Now I tell people the prices start at $225. If they think thats high I dont have to waste a trip to see it. It takes a while to get the hang of it but I can guess within the hour now.
The easiest clean ups are blow in the woods.
I would never bid by the hour either. The client has no way of knowing how long it will take. A lot are surprised on how fast we're out of there and dont care that they forked over $400 for 3 hours of work because they spent hours raking and not even putting a dent in the yard.