Thanks for getting back here, @1440qb-gmail-com.

In QuickBooks Online (QBO), you can create a schedule for when to email an invoice when you use the recurring feature as outlined by Mark_R. Since you need to invoice your client every Friday, you can set the recurring template Interval as Weekly. You can also set a Start date and End date depending on what you and your client discussed. 

For your reference, please see this article: Schedule recurring transactions.

In case you want to have a list of your customers’ outstanding balances, you can run the Accounts Receivable aging summary report. This report will show you how much are still due and how long they're past due.  

Feel free to post again here if you have additional questions creating an emailing schedule on your invoice. I am always around to give you a hand. Have a good one.