What age is a schnauzer housetrained?

by hannah
(london, england)

I am looking to buy a miniature schnauzer. I would like a schnauzer that is already housetrained, at what age could I expect this in a dog? Also, do you know how long a miniature schnauzer can be left alone? I work from home but occassionally need to leave the house for 3-4 hours.

Thank you