Thank you for posting in the Community. I'll share some information about managing your rental properties in QuickBooks Online.
Yes, you can use the project to separate costs from one rental to another. Project feature helps you to track and calculate your income and costs and stay organized and trace all the moving parts. You can add project income and expenses, tag old transactions to new projects, and run project-specific reports from a single dashboard. To start with, I'd suggest turning on this feature on the Account and Settings page. Please note that this feature is only available in QuickBooks Online Plus and Advanced.
Click the Gear ⚙ icon. Then, select Account and Settings.
Go to the Advanced tab.
Find the Projects section and click it to expand the page.
Choose the Organize all job-related activity in one place checkbox.
Hit Save and Done to close your settings.
Once done, you can now start creating a project. Please follow the steps below.
Select the Projects menu.
Click the New Project button.
Give your project a memorable name.
Select the customer you’re working for from the drop-down menu.
Add any notes or details about the project.
After that, start adding income and expenses to your project. Adding transactions to projects won’t change how they’re categorized or affect your books. To see additional information and steps, you can open this article: Set up and create projects in QuickBooks Online.
You also have the option to use class tracking in QuickBooks Online. This feature helps you manage your transactions by business segment. This is beneficial for reporting purposes to see how one division of a company is doing compared to others. For additional information about this feature, you can click this article: Get started with class tracking in QuickBooks Online.
Please refer to this article to see steps on how to run reports to view sales performance by class: Run reports by class.
Please know that I'm just a post away if you have any other questions about processing rental properties in QuickBooks. I'll be happy to help you out. Have a great rest of the week.