rootX said:
I will be working in NYC for four months at the bottom of Central park

.
I am soon starting to find a room that is close to my work/easy to commute from but wanted to know:
The Central Park South area is where the Owners of the World reside. Those are the Upper East Side, Lower East Side, and Midtown neighborhoods. Here is an income distribution map for NYC; should give you an idea of whom your neighbors are going to be.
http://envisioningdevelopment.net/map
rootX said:
- For the rental, how low I should aim for? (I couldn't find anything below 1200/month for one room, which I find bit expensive but *expected)
Anything below $1000 is going to place you at least 20 mins outside Manhattan (subway). The $1000 - $2000 range might get you something decent to comfortable in Washington Heights, Brooklyn Heights, Park Slope, Astoria, and Woodside.
Washington Heights is in the lower range. It is mostly a Dominican neighborhood undergoing gentrification by young white college students fleeing the higher rents a bit further south; it generally a safe area but it is very dirty (lots of garbage). Astoria and Woodside are mostly in the middle of the range, and those two are a mix of young college students, immigrants, working people, etc. Very good restaurants in this area. Park Slope and Brooklyn Heights are in the higher range, and these neighborhoods are mostly composed of young professionals who may or may not have families; good number of college students, too.
Neighborhoods to avoid: Harlem, Chinatown, anything east of Crown Heights, anything near Yankee Stadium. All those neighborhoods except Chinatown are still somewhat dangerous at night; Chinatown is packed with people, and a tourist trap.
rootX said:
- If the island is expensive could it be easily commutable from outside.
Yes. The D, N, Q, R, and 7 subway lines are your best friends. Avoid the 4, 5, and 6 lines at all costs, else you will hate your fellow human beings (trains always crowded).
rootX said:
- How safe it is to use public transportation during late hours like 12 AM
It is generally safe throughout NYC, especially in Manhattan. If you need to take the train at night, ride in subway cars that already have people in them, especially women.