What is the equivalent of netsh wlan hostednetwork on MacOSX?
I think this is not possible. What do you try to archive? If you have the login credentials for the network your first mac uses, you could use those on any other device to connect to the wlan. The only thing I could think of is using a mac as a repeater. Questions regarding this were answered at: MacBook as WiFi extender and Macbook Pro as a wireless bridge? (Private hotspot from external wifi connection)

tl;dr: It is not possible. one solution is to use another external wifi card via usb.