You need to add up everything you pay from rent to gas to replacement cost and maintenance cost on your machines taxes etc. Then divide it by however many weeks the season is there and divide it by 40 thats your hourly rate (basic). Imagine how long it takes to mow the yard your talking about and you can get an idea of what it cost you. Now you just need to figure out a good profit margin that is competitive yet won't scare people away. Here a normal lot goes for 70 per month or about 20 per cut (weekly). Thats a 60x100 lot around 1/5 of an acre I believe. Mowing, edging, line trimming minor herbicide and blowing.