The hobo camp that Montag finds is simply a cleared spot by the railroad tracks where the men have made a fire. They are transitory, moving around to avoid detection, so they carry their gear with them and don't remain in any one spot for too long. Montag focuses on the campfire, which is different than fire in his experience; the fire is warming the men instead of burning them.
There was a silence gathered all about that fire and the silence was in the men's faces, and time was there, time enough to sit by this rusting track under the trees, and look at the world and turn it over with the eyes, as if it were held to the centre of the bonfire, a piece of steel these men were all shaping.
(Bradbury, Fahrenheit 451, Google Books)
They also have a portable TV, which they use to watch Montag's chase. Montag, bred of the city, finds himself comfortable and even happy in their company; he has no comprehension of this sort of life, but in its simplicity he finds something he lacked in the city. Once the city has been destroyed, they pack up and walk back towards the city, to help survivors and try to rebuild civilization.