Which one of the following is correct:
What do residential areas in a big city look like, and who lives there?
What do residential areas in a big city look like, and who live there?
There are more people there, so would "live" be correct?
This is a compound sentence. Try breaking it apart.
What do residential areas in a big city look like? Who lives there?
"Who live there?" would sound wrong, no? While "who" might refer to many people, it is treated as singular in an interrogative where the verb acting on the interrogative pronoun isn't a form of "to be".
If that verb is a form of "to be", then the verb agrees with the number of the predicate.
Saying who lives there is correct. You can't say who live there, however you can say those/the ones who live there but that would change the meaning as follows:
What do residential areas in a big city look like, and who (meaning "what kind of person") lives there?
What do residential areas in a big city look like, and [what do] those who live there [look like]?
"Who lives there" would be correct, but the "who" implication for the listener should be understood as "what kind of people"; such as, "well-to-do professionals", "construction workers and lumberjacks", "poor Haitian refugees" or whatever
This is a very intelligent question.
If I recall all such sentences, I see that 'who' in itself is singular. That's because if you ask a simple question,
who ______ there? The obvious verb there is 'lives' and not 'live'.
On the other hand, if provided with some context, 'who' can address to a plural word as well.
I'm referring to those who are wearing red tee.
Having said that, 'who' on its own seems singular, but provided with context, can serve to a plural word as well.