Is it possible to send an estimate to a customer for products that aren't owned by my company yet? I will buy them only if the customer accepts the estimate.

Hello there, nabatman-ye-gmai.

No, that isn't possible. The estimate will not be considered a transaction until your customer accepts it and is converted into an invoice. You'll need to select an existing product or add a new one to create them. You can check out this article for more detailed information: Create and send estimates in QuickBooks Online.

Additionally, you may also personalize and add information to your sales forms. I've included this resource to learn about changing the layout of your sales forms so customers only see information that matters most to your business. Customise invoices, estimates, and sales receipts in QuickBooks Online.

If you have further questions about the estimate, just add any details below. I'll get back to you with more information.