He doesn’t spend much time with friends
And if he doesn’t, he will expect you not to either. Pay attention at dinner to see how many (if any) stories he tells about fun things he has done with his buddies recently. See how many of his stories in general involve friends, and if the friends are consistent (i.e., can he keep friends?) If this guy doesn’t have a social life, he will expect you to be his social life. And he won’t be happy about you having your own.