You have two options for the motorhome when it's in freezing weather (assuming it's a cold weather capable unit, i.e. the plumbing is enclosed within the heated part of the motorhome). Either you keep the motorhome heated above freezing, using say the furnace or by storing it in a heated indoor storage facility, or you winterize the plumbing system.
Winterizing isn't hard and the materials required aren't that expensive. If you have an air compressor and so can blow out the lines with air, the materials are downright cheap--just sufficient RV antifreeze to put a cup in each of the drain traps. If you instead displace the water with antifreeze in the pipes, it could be a couple gallons or so, still not very expensive.
I use the compressed air method with my motorhome. I start by draining the fresh water tank, the plumbing as much as practical with the low point drains, and the water heater; this means opening a few valves and the various taps on the sinks etc., removing the water heater drain plug, and then going away for several minutes while water dribbles out onto the ground. Next, I bypass the water heater, run the pump for a bit (to get water out of the suction lines and pump body as much as possible--it's OK to run RV water pumps dry for a minute or two), and hook up the compressor to the city water inlet via an adapter I pieced together. The compressor's regulator is set somewhere around 40 psi. Next, I successively open individually each of the taps and the low point drains and let the air flow until no water drops are spitting out, usually going around a couple of times. Then it's just disconnecting the compressor, shutting valves, and pouring a cup of RV antifreeze down each drain and into the toilet bowl, and draining out the bit of water I just put in the holding tanks.
All told, it's maybe a half hour of work and a dollar or two of RV antifreeze. Dewinterizing is equally as easy: put the plug back in the water heater, unbypass it, and sanitize and fill the water system. I do usually try to check for leaks beforehand with air pressure. The check valve in my city water connection vibrates when air flows through it, which makes checking for big leaks fairly straightforward: just listen for that sound.