My 2 Cents
When I devised my business plan, most of the forecasted numbers were hypothetical based on my competitions price scales. It is true the more diversied your services, the more revenue available. I highly recommend focusing on other revenue streams once you establish your core set of services.
If you plan to mow, edge, fertilize, etc.... Than make it your core services and provide the quality work expected.
Then, add to your services with your base set of clients. Services such as Mulching, Landscapes, Aeration, etc..... You can also advertise other services to potential clients however your marketing efforts could differentiate from my own.
Be Realistic. Revenue Streams take time to generate. Take a lot of a little in order to keep money coming in the door. Extensive research via phone calls to your competitors is definately an ideal situation. Find out what they are doing, how they market, services they offer etc.... (Pretend to be a business student). Find out how they built the business and adjust your plan to do it better....