At a loss for realistic characters? You need look no farther than your local coffee shop. Local coffee shops have a resident population that is a microcosm of wider society. The coffee shop where I hang out (which will remain nameless for obvious reasons) has a rotating cast that would work well in your novel or short story.
One player is the knucklehead: the kid who’s there every day soaking up the wi-fi, but never buys anything. Never. It’s not that he’s short of dough. He’ll buy a two foot long poorboy sandwich and a can of soda at Safeway, then head over to the coffee shop and hang out for hours munching on the sandwich and bugging the staff.. Independent coffee shops survive on their clientele, but this guy stiffs the shop and the employees. There’s got to be a reason why—Nobody can be that obtuse—I just haven’t figured it out yet.
Then you have Bill and Harvey. Bill holds court in the coffee shop every day, opining in a loud voice about whatever topic crosses his mind. He’s an authority on everything and absolutely nothing. His foil is Harvey. Harvey’s an older feller, can’t see too well and his health ain’t that great. Here’s a recent exchange.
Bill (quite loudly): Harv, you’re in bad shape. You’re blind in one eye and can’t see so well out of the other.
Bill: You should do something about that. Oh, right. You can’t
Bill: And that bad ticker of yours. You ain’t got long to live, Harv. Not long at all.
Actually, I haven’t seen Harvey recently. I hope Bill’s prediction hasn’t come to pass.
Of course there are other characters: the 65 year old drama queen, the couple that sneak in and steal the house newspaper and leave thinking that no one notices, and the bombshell that has a crush on the male barista who is a truly nice guy. They’re all waiting for you to write them into a story.