I’m new to selling a car. If the buyer wants to take the car to his/her mechanic, am I suppose to ask for a deposit? For how much? The person will need his/her license to drive to the mechanic, so what else can I ask for?
Thanks!
I would just ask for the keys to his car. 
You could ask for a small non-refundable deposit If he or she decides to buy the car the deposit can be deducted from the price of final purchase. Of course, the buyer should also pay for the inspection.
Ditto…
Just drive it to his mechanic on a Saturday. Don’t accept the keys to a stolen car.
I agree. Just arrange a time that would be best for both of you, drive over there and chit chat some while you’re waiting. let them know about anything you’ve done to the car maintenance wise while you’ve owned it. Any history of problems you’ve had recently, or in the past. Give 'em a history lesson on the car, who you bought it off of, etc.
Take a digital picture or scan/copy of their license front/back.
Taking a non-refundable deposit is a bit much as suggested. If your uncomfortable drive the vehicle yourself to their mechanic. Yes all the PITA of selling your own vehicle however it can yield at least $1000 for a few - many hours of your time.