How to avoid this "friend"...URGENT?

You assume he will bug and argue but you dont know that for sure. As for your reasons they must not be very good ones to want to end a 10 year friendship or you would have just mentioned them. IF its a case where you have different interests then him and like to do different things then i can completely understand and by all means just tell him instead of trying to avoid him its not fair to him or yourself. Just be honest ...brutally IF being nice doesnt work at first