What do you mean "teach it to use the litter box"?!? You're getting a HUGE dog, not some small froo froo dog, right?
With older dogs, housetrained dogs, they can do just fine without any routine. My doggies don't crap on a schedule, but if I wake them up too early, sometimes they won't even go outside. I tell you, you get the dogs that are right for you, no matter which ones you get.
But after a while, you should be able to predict how long after eating the doggy is done "processing".