I use a Google Voice number for advertising unit listings. It still rings to my personal phone, but I know immediately that it's not a personal call so I can decide whether to take it or send it to voice mail. I note in the advertisements that a google voice number is used for privacy reasons so potential tenants don't think the number is a scam (it announces to the caller that it IS a google voice number). This way, when the unit is no longer available, I can uninstall or disable the google voice app until the next time I need it so that I'm not getting applicant calls long after the ad has been taken down.
I decided not to use a Google Voice number for my tenants to contact me with (for repairs or other issues) because it doesn't allow pictures to be sent through text messages, my preferred method of communication.
I'm only managing 4 units and I live on the property, so while Google voice is a good solution for me, it may not be for a larger property with more units.