Weekly scheduling vs monthly Invoicing
Weekly repeat scheduling of a job is very common. Regular invoicing is typically a standard fixed time - first of the month or end of the month. The problem is that not all months are equal. Repeating a job weekly will not always fall nicely at either the beginning of the month or the end of the month. Also, repeating weekly jobs are not always equal in number from month to month. Some months have 4 weeks and some months have 5 weeks and depending how the weeks start or end in a month you may end up with only 3 full weeks in a month. This makes it very difficult to manage invoicing.
In this case consider creating a separate line of jobs strictly for invoicing.
For this scenario I have created a 'service' or job title that states exactly what the series is for - "Monthly Invoice". I then create the job, create the start date for the date that I will want to send out my first invoice, assign task to my A/R person, and put in the fixed charge(s).
Lastly, from that starting date (beginning series) I then click "Repeat this job" from the schedule line and schedule this job to repeat monthly.