One guy wanna buy my car by cashier check

Hello everyone,

I’m currently dealing with a buyer on Marketplace. My car is valued at $20,000. He said he is willing to issue a cashier's check from what he claims to be a military credit union and will provide its invoice. He also agreed to meet me at my bank on the day of the transaction and let the banker verify and deposit the check.

Do you think this is safe? I’m concerned that the check might take a long time to clear or eventually get rejected, which could result in a loss for me. Should I ask him to use a wire transfer instead? I’d love to hear your opinions. Thank you!