This might sound like a stupid question, but can a homeless person even get a job? Isn't the whole cycle of becoming homeless evil because you need a residents to apply for a job? Just like all those freelance website require you to link a bank account which you need a address to get a bank account.
I am not having too many problems with that yet. And yes, I can use the shelter as a mailing address. Though I just use the address on my ID, which I no longer live at, for fields where they just need an address but won't mail anything to me.
A homeless shelter, a day center, a church, a sympathetic friend. My local indie book store allows homeless people to use their mailing address. Finding someone who will hold your mail is a lot easier than finding somewhere to live.