Honestly, I think you'd do better by either posting flyers in local stores, or handing them out in neighborhoods where you see people doing their own mowing. Half the expense of any small business like that is travel, and the closer the clients are to each other, the better.
Craig's List can also be dangerous - just stick to a neighborhood tat isn't so high-level as to already have landscaping all booked, and you'll get more responses, and not be driving and unloading so much. Post in the library, hardware stores, coffee shops, and sub shops.
