Hello, TheDoctor165,

Welcome to the Community and thanks for joining the thread.

Let me share information about the Item types available in QuickBooks Desktop.

The items set up into your account shows up as a line on an invoice or other sales forms. Upon adding items, QuickBooks provides different item types that you can choose. For guidance in setting up, you can check out this article: Add, edit, and delete items.

As for your question if you'd add rental units as products, services or leave the products and services empty, I'd recommend reaching out to your Accountant to ensure that this items will be track and accounted properly.

For future reference, I'm attaching a great resource that you can check: Create a property management company.

If you have further questions, please feel free to visit the Community again. Have a great day!