Labour Rates are defined as Billing Rates in Tradify and are set up under Settings > Pricing Levels & Billing Rates.
Any number of Billing Rates can be created and these can be selected by the Staff Members at the point of adding a Time Entry on a Job. Each Billing Rate can have it's own hourly charge out rate.
To create a Zero Charge out rate for a Billing Rate, simply add a Billing Rate by clicking on the "New Billing Rate" button at the bottom of the Pricing Levels & Billing Rates window. Enter the relevant details as required for the Billing Rate and then place a tick in the Check Box entitled: "Let me enter the price later" as shown below.
This will allow the Billing Rate to be saved with Zero Hourly Rates.