I was homeless this year from January 2 to early April and let me tell you it was a brutal winter in NY. I didn't have a car so my only option was a homeless shelter. The dinners were decent but other than that I only got a bowl of cereal in the morning. It was impossible to get a job in that situation because in order to stay in the shelter I had to get dropped off at welfare every morning to file paperwork that I need housing, and then sign up for the van back to the shelter at 2pm, then the van would finally come at 5, so there was no time to work.
I finally got moved to a different temporary shelter where I could stay during the day and there was food, so I could work from there. They were really strict though and I got kicked out for breaking curfew once, and just went back to my parents hanging my head.
I second what several people have said about libraries being a great resource. There's actually a decent amount of homeless people there during the day, but the average person couldn't tell. For food, try churches. Most of them have outreach programs (which could help you with a job too), and I had access to a food pantry at a counseling center too. Foodstamps help but when you are homeless the money goes fast since you are forced to buy a lot of single serving food items due to not having any refrigeration, and those cost a lot in comparison to buying in bulk. My stamps came out to just under $7 a day, which really isn't much if you are buying 3 meals a day with it, and trust me you need a lot of food for energy when you are homeless and have to walk long distances everyday.
Department of Social Services will pay a little if you find a cheap place to rent, but the place has to accept their method of payment and be approved by them. They didn't pay enough for any rooms I saw for rent, but a few people I was in the shelter with finally got placed in one of the rooms of houses that DSS worked with, but most all of them had roaches, bedbugs, 3-4 people per room, and your property wouldn't be safe there if you left the house at all.