As someone who lived in NYC for a while circa 1999 the process at the time as I recall it was using a newspaper classified ad to find a broker to find an apartment.
The vast majority of actual apartment listings were all gatekept within the broker system making hiring a broker (with an insane fee) effectively mandatory for actually finding a place to live in a reasonable timeframe.
I had the funniest experience with brokers in mid-1990s Silicon Valley.
I was shacked-up with my girlfriend in an ADU garage in Santa Cruz. She was willing to move out with me and some roommates. So the four of us went apartment-hunting in the South Bay area. We eventually found a house in San Jose. It was a dilapidated old property in a ratty area of downtown, but it was our humble home.
Anyway, we had discovered this great concept of apartment brokers who would do the legwork for us! So we signed up to one. Now everyone had computers, but the Internet was for blogs, porn and cat pictures, so nobody did actual work or business over the Internet! So we would go in-person to this brokers office and they would help us fill out paperwork and stuff.
And I have this one, extraordinarily vivid memory of standing there, sullen nerdy goth me with my perky goth artist girlfriend, and we're at the front counter in a small lobby, blinking slowly at two young lady brokers who are standing at their computer terminals, typing earnestly, and they informed us of some computer outage, but the systems are coming back online and these girlbosses are the ones saving the day.
And they begin typing even more insistently and firmly, and they're just banging on the keyboards like there is no tomorrow and they really, really need the systems back in order, and there was just a palpable sense of urgency and naïvete mixing together in the air of this business, and finally these blonde girlbosses chirp that they found us something! And at that moment we embraced and we could practically hear the theme song to "The Jeffersons" playing in the background.
That is the only time that an apartment-finding broker found a place for me, but I have believed in the service type ever since. I am sure that if we had been better people with money, they could've found a good place to live. It was heady times in SV for sure.
Brokers still gatekeep the best inventory in NYC for the most part.
Every craigslist apartment I ever found was sketchy as hell.