Stepdown resistors should go as close to point of use as possible so as to obtain proper voltage and amperage. You won't know the amount or size of the resistors until you see what your loss is from the DC over distance.

ie.
You have a solar panel bank set up on your garage roof because it gets better sunlight. So you keep the battery bank there as well. If you want to run an inverter you would go straight from the batteries to the inverter and then do a line to your house with no resistors because there is almost no loss in AC. If you want DC only then you run from the batteries to an automatic regulator at the house because of the loss from running the distance in DC plus the variance in the voltage of the batteries would change the amount of resistance you need. So you can't use a static resistance system and you would have to make the voltage far greater because of the drastic loss. (am I making sense?)