Funny ... so far as I know, residents here take great pride in tending to their own gardens.
Unless of course you live on property that has an enormous landscape, then the Business Pages are your friend.
I suppose you could place an ad in your local paper, much like those looking for babysitters and putzfrauen.
As for what to charge per hour. What can you afford?
Try networking a bit and asking your neighbors/co-workers what they might charge ... even better if you get a recommendation.