to my knowledge, it is usually not a good

idea to pay the lunch for him. Taking lunch together, chatting together will certainly help to make a good connection. Nobody is short of 1 lunch; that amount of money is nothing. However, having chance to sit together is more important.

After saying so, i realize that everybody will be different in the world. Maybe you can ask after or before the lunch that u will be happy to pay for him. If he says no, do not insist at all.