Have I mentioned how much I really really like my sleeping bag?

If you’re homeless, or living in your vehicle, invest in a good sleeping bag.

I’m not talking about the walmart camping aisle special.
A good sleeping bag. Something that you can cinch down over your head. Something rated to at least 10 degrees; if you live in the frozen northeast find one rated as low as you can.

Also invest in a silk sleep sack. Get the same shape as your sleeping bag, likely a mummy style. A sleep sack can add up to 10 degrees warmth.
And just as importantly, a sleepsack will keep your sleeping bag cleaner (and therefore warmer). You can wash the sleepsack easily, a sleeping bag is much more expensive and time consuming to wash.
A sleep sack made of bamboo is also a good option.
Stay away from cotton; these are good for hostels or hotels, but not great inside a sleeping bag.

People who don’t know any better may tell you that you should be spending that money on food or a cheap hotel or who knows what.
Food you can buy with food stamps.
A cheap hotel is a limited option.
But a good sleeping bag can keep you alive AND let you sleep well, essential if you’re still trying to stay connected to, or reintegrated with, society.

To see what’s available check out http://www.rei.com or http://www.backcountry.com and plug sleep sack into the search field.
These are also good sites to see and compare what sleeping bags are available.