How do you house train an older dog?

We adopted a little Lhasa Apso who is an unknown age, although he does have grey hair around his nose, eyes and mouth. He wets ALL over the house, I find 8-10 puddles every day. He wets on clothes baskets with clothes in them. He wets on my kids beds, on the couches, everywhere. We take him out every hour and for two walks, one in the morning and one in the evening. We have had him for a few months now and it isn't getting any better and I am at a loss as to what to do. We have five kids and I can't have dog urine everywhere. One of the agreements when we adopted him was that he wouldn't stay outside for more than a couple hours, plus we live in Arizona and it is already really hot here, outside just isn't an option.