A lot of people feel like urban fantasy is a shortcut that gets you around world-building, because it's set "in the real world." But it doesn't really work that way, as I found out. You have to come up with just as consistent an internal cosmology and magic system as you would if you were writing high fantasy.
Cassandra ClareYou screamed.” Will said. “Is that all you did?” “I screamed a great deal.” Tatiana sounded injured.
Cassandra ClareBitten? You mean you're a-" "A werewolf," said the girl. "Like everyone else here. Except you, and the asshole. And the asshole's sister.
Cassandra ClareBut how do they get inside?" "They fly," Jace said, and indicated the upper floors of the building. [...] "We don't fly," Clary felt impelled to point out. "No," Jace agreed. "We don't fly. We break and enter." He started across the street toward the hotel. "Flying sounds like more fun," Clary said, hurrying to catch up with him. "Right now everything sounds like more fun.
Cassandra Clare