It's best to start as early as possible. There's no such thing as too early for house-training, even if they aren't going to be pros at it at first. In fact, the earlier they start, the easier it'll be for them once they are able to hold it, since they won't have acquired any bad habits.
The best thing you can do is watch them constantly while you are home, so that you can watch for signs of them having to go (sniffing, circling, squatting, etc.) The less accidents they have in the house, the better.
If they do have an accident, then you have to use special enzymatic cleaner on it made for dogs, so that they don't return to the spot. Unfortunately, regular household cleaners won't cut it, since dogs have amazing noses that will be able to smell the tiniest bits of pees that the cleaners leave behind.
You need something like this:
Amazon.com : Pet Odor Eliminator & Pet Urine Cleaner: Professional Strength Enzyme Cleaner - More Powerful Than Natures Miracle Urine Destroyer - Best Odor Eliminator - Cat Urine Odor Remover and Dog Urine Remover- Pet Stain Remover - Best Urine Neut
Whenever you aren't home, they need to be in their crate. However, do not leave them in there, unless you are confident that they can hold it for the amount of time you'll be gone. If they learn to potty in their crate and be near their waste, it'll be very difficult to housebreak them.