by the way, there are always people that switch to another program at the start of the second year to another hospital. That's my understanding. When we were at orientation there were new people starting IM PGY 2. So my question is, how do I find out out what programs are willing to take a future PGY 2 IM in nyc.
In your first question, you appear to be asking about trading positions with another PGY-1 in IM. You cannot just trade positions without program approval and approval of the NRMP for you to break your match contract. The final approval is up to the NRMP, not you or the program.
Switching, ie, moving to a different program without "trading" the spot with another resident, is an another matter entirely if done after the PGY-1. Many people move around programs - either because they only matched into a Prelim PGY-1 (and hence would move for the categorical PGY-2), or for personal reasons.
Semantics aside, there is a real difference btwn trading a PGY-1 position and transferring (switching) into a PGY-2 program.