ChemLeg

I can't say anything about SanFrancisco, but I know a bit about New York.

The transit system was built properly for the most part - subways aren't too crowded, and if you live far enough away (long commute), it usually means you get a seat (sleep, read, study).
 
Rent is horrendous in Manhattan, and usually not worth it. Brooklyn and Queens strike a good balance of safety and rent, as long as you stay out of the worst neighborhoods (Bed-Stuy, Brownsville), and areas that are "up-and-coming" for absolutely no reason.
 
http://mta.info/maps/submap.html
 
A good indicator for wealth in Brooklyn - if you live along the number lines, you are probably not good for one reason or another. Either because it is super expensive (Prospect Heights), or you are in the projects (East Flatbush)
Along the letter lines, south of Prospect Park (but just outside of Coney Island), you are actually okay. You know what, do yourself a favor - avoid anything north of Prospect Park, east of where the M-line turns north. Bed Stuy, Brownsville, Bushwick are all places to avoid.

Queens is also nice in most areas, but transit is a pain, so that will be more of a consideration. 

Good news is, there's a bunch of cheap food, including Chinese, Tex-Mex, Pizza (I promise you will be in heaven compared to California) or if you go into the ethnic neighborhoods, their delicacies (Russian, Polish, Italian, Caribbean, Indian), or for the lunch-rush, the Halal food carts (which have a lower chance of rat feces and roaches than most of the restaurants). 
And no, you don't lose out on your produce - I still get my avocados for a buck, Pomegranates are around. Actually, you might have a nicer selection because we have different groups that can guarantee demand for supplies, so we have a constant steady stream of foods that would otherwise be unavailable. 
 
 
It is possible to live here, you just need to pinch pennies and room with 2 or three other people, and accept that you will not have space for your belongings, so take the bare minimum you can. 

I can't say anything about SanFrancisco, but I know a bit about New York.

The transit system was built properly for the most part - subways aren't too crowded, and if you live far enough away (long commute), it usually means you get a seat (sleep, read, study).
 
Rent is horrendous in Manhattan, and usually not worth it. Brooklyn and Queens strike a good balance of safety and rent, as long as you stay out of the worst neighborhoods (Bed-Stuy, Brownsville), and areas that are "up-and-coming" for absolutely no reason.
 
http://mta.info/maps/submap.html
 
A good indicator for wealth in Brooklyn - if you live along the number lines, you are probably not good for one reason or another. Either because it is super expensive (Prospect Heights), or you are in the projects (East Flatbush)
Along the letter lines, south of Prospect Park (but just outside of Coney Island), you are actually okay. You know what, do yourself a favor - avoid anything north of Prospect Park, east of where the M-line turns north. Bed Stuy, Brownsville, Bushwick are all places to avoid.

Queens is also nice in most areas, but transit is a pain, so that will be more of a consideration. 

Good news is, there's a bunch of cheap food, including Chinese, Tex-Mex, Pizza (I promise you will be in heaven compared to California) or if you go into the ethnic neighborhoods, their delicacies (Russian, Polish, Italian, Caribbean, Indian), or for the lunch-rush, the Halal food carts (which have a lower chance of rat feces and roaches than most of the restaurants). 
And no, you don't lose out on your produce - I still get my avocados for a buck, Pomegranates are around. Actually, you might have a nicer selection because we have different groups that can guarantee demand for supplies, so we have a constant steady stream of foods that would otherwise be unavailable. 
 
 
It is possible to live here, you just need to pinch pennies and room with 2 or three other people, and accept that you will not have space for your belongings, so take the bare minimum you can.