When you say you want it cleaned out to sell, are you talking just your info from the drive, or actually opening the Macbook Pro up and cleaning the insides? Physically opening the 2016 MBP can be a difficult for someone who doesn't have the right tools or knowledge.
I would instead just erase the drive myself and reset it to factory settings. Make sure you have all of your files that you want to keep backed up before you begin. Go to this guide What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
Skip down to the area that says "If your Mac doesn't have Erase All Content and Settings" because your MBP doesn't have Apple Silicon or a T2 chip.
Going into recovery means to turn off the computer, then to hold "command" + "R" when you press the power button.