There's AQUALUNG from Jethro Tull, which might have a bearing - I particularly like the last two lines. But it is kind of bitter and aggressive (and possibly the old man isn't even homeless, but I think he is).

Sitting on a park bench
Eyeing little girls with bad intent.
Snot is running down his nose
Greasy fingers smearing shabby clothes.
Hey Aqualung. Drying in the cold sun
Watching as the frilly panties run.
Hey Aqualung. Feeling like a dead duck
Spitting out pieces of his broken luck.
Oh Aqualung.

Sun streaking cold, an old man wandering lonely.
Taking time the only way he knows.
Leg hurting bad as he bends to pick a dog-end
He goes down to the bog and warms his feet.
Feeling alone, the Army's up the road
Salvation a la mode, and a cup of tea.
Aqualung my friend, don't you start away uneasy
You poor old sod, you see it's only me.

Do you still remember December's foggy freeze
When the ice that clings on to your beard was screaming agony?
And you snatch your rattling last breaths with deep-sea-diver sounds
And the flowers bloom like madness in the spring.