How long can someone stay there, I am 58 yrs old don't have family, been on the streets for five years

It depends. If you're just trying to stay off the streets it's a night to night thing like most places. However if you're genuinely trying to recover they have a mentor program that can last a long time.

What programs they have at Union Mission?

I recommend Austin Street. It's more suited for people over 50.

Are you a honorable discharge veteran?