How would you judge if someone refuse to use escrow his reason ro refuse is that 20$ is a small amount of money.
I am cautious because people here will try to scam 0.01$ if they get the oportuinity
He is probably trying to scam you because of refusing to used an escrow. And eventhough its just $20 that you are saying a lot of scammers will likely take it. And believed me, there are hundreds here who have been scammed much lower than $20 because they trusted the other party. So you have every right to be cautious and try to used escrow so that you will prevent yourself from being scam. And if refuses, then don't do the trade, simple as that.
I don't know why he won't just go with the escrow. They don't take much fee and it really is worth it for that insurance.
Use an escrow that is well known. I know some scammers send you to a scam escrow.
I wouldn't risk the $20