Any time that you can get clients signed up is great. Try offering a one time service such as aeration or leaf clean up can work wonders for signing people up for a maintenance contract. We signed up 75% of our maintenance clients this way.
Rate all depends on how long it will take you to do the yard and how much it costs you to do the yard plus % off other expenses such as truck and company insurance.
Its all in the numbers, the more flyers, postcards , emails, etc you get out the more return you will get. Dont rely on other people to get you business, go out and market your company. Do that and you will soon have all the business you want. Good luck