I scored a 600 square foot one-bedroom sublet on upper west side for 1200/month off CL. Just requires a solid week of calling everything. Only thing it only lasted 10 months until the girl broke up with her BF and needed the apt back.
As for downtown you need to be specific…Below 14th? Below Houston? Tribeca? Financial District?
600-800 square feet is going run 3-5k/month depending on the building and amenities. I have few friends that work real estate in the area…shoot me a PM if you would like their contact information
He’s look at Central Park South / Columbus Circle. He doesn’t care that much about price, just wants to get a good deal. For example, if realtors are trying to show an 800 sq ft 1 bedroom for $5K/month, he knows he can find it on his own for ~$4.25K or less with persistence. But he just needs to know where to look.