i'd get a sublet off of craigslist.org as well. some of the cheaper manhattan neighborhoods like chinatown/east village or upper east side (not talking park av., but more like 1st avenue) may work for you. as for philly-nyc:

if you're a foreign citizen, u may be able to purchase an amtrak pass (then we start to get into their definition of "commute") but amtrak is notoriously unreliable.

SEPTA/NJ may work, but a long commute.

chinatown bus, subject to traffic conditions.

if sublet is absolutely not an option for you (i'd imagine u can spend about $1,000 for a room in a 3-br or a 2-br in Upper East Side), i'd go with SEPTA/NJ for reliability.

but $1,000 for 4 weeks for a sublet wouldn't be bad, given the transportation cost and your time and stress.