Just to be clearer, you are creating a job first. Once you have the job you create a scheduled work event. The event is what is assigned to your tech.
Then, once the work is completed you should have your crew member (technician) mark their assigned event complete.
Now, you can coordinate with your crew that once their event is completed you can agree that you will mark the entire job completed.
You should be managing the job statuses each day and extending or rescheduling for additional days and hours each day. I would then suggest you mange the calendar view each day or the resources calendar to see if the scheduled work event has been marked complete.
If the only scheduled work event or last scheduled work event has been marked complete you or your staff can mark the entire job complete.
Once that process is in place all you have to do is manage the Completed Jobs column here:
You could decide that you are going to be the person to actually generate the invoice and email it to the client.
Once the invoice has been emailed then it is just a matter of Accounts Receivables (A/R) collections.
Tip: Keep each of your job page columns updated