I don't think I could do this kind of work if it was year round. In my area it's lawn services from the middle of March to the middle of November. I'm in bad need of a break by the end of the season. There are people who do snow removal here but the snowfall is so uncertain in my area I've never wanted to be bothered with it.
As for billing it's per service. The jobs are either weekly or bi-weekly and unless it's raining big time I show up on the appointed day. Additional services are billed whenever they are performed. I do have some weekly customers that get billed every other week just for convenience.
I know another LCO who bills all customers at the end of the month for whatever services were performed during that month. How can you wait that long for your money?