I am in a service based business. How do I create an invoice but not invoice (until later) I need the price to save but not invoice until ready.

Go to the gear icon, lists, and recurring transactions to create a "recurring" invoice and specify the start date as the date you would like the invoice to be created. You can set an end date or have it become a scheduled recurring invoice.

To document the price but not create a sale yet, use Estimates.

An Estimate is also an option, however, the Estimate will need to be converted to an Invoice at a later date, so it would not be my first choice, especially if the customer has already agreed to the service and price, as this would be extra work. You would have to approve the Estimate and convert it to an Invoice. The creation of a recurring invoice for services that have already been approved for a later date would take fewer steps in the accounting process.