We do not currently have plans to add Renter/Landlord to the Buyer/Seller field. However, there is an option for tracking rentals by using filters.
In the Transaction, form enter Yes or No in the field labeled Rental. This is the best place to track whether a transaction is a rental or not.
To track this information, you can create a filter on the Transactions tab.
In the Filter menu, you will need to scroll down to the Yes/No field, which is the fifth from the bottom. In the dropdown select Rental and then select the Yes circle and click Filter. This will show you only transactions that have the Rental field filled out with Yes. Then you can save the filter as new to be able to select the Rental filter from the Transactions dropdown.
If you need to be able to view your transactions that aren't rentals, you can do the same filter process but select the No and Not Filled circles instead.