I retired from a Freightliner dealer and we also worked on Freightliner chassis motorhomes, which isn't revelant but is in a way.
What I noticed most was the low mileage motor homes had issues related to cooling systems and consumable components like fan belts, seals, exhaust systems, tires and brakes.
Whether the unit is being used or not, the components are aging, seals are drying out and leaking and a parked unit, especially one parked on dirt, the ground moisture is always rising up to corrode chassis components and exhaust systems.
Never saw any with a blown motor but I saw plenty of fan clutches, fan belts, siezed alternators and a whole raft of rotted out exhaust systems, some brake issues (hung calipers and leaking wheel cylinders, all attributable to age and not to mileage driven.
If it's older with low mileage, it did a lot of sitting and components age, sitting or being used.
The other thing you need to do is inspect the unit for water intrusion. If it sat mostly, did the original owner keep after the seals and caulk? Water between the inner and outer walls can cause rot and mold and if it's a FR coach, most of the above the chassis framing is wood. Wood rots when it gets wet and where you are at (in BC) you get weather and moisture.
At the very least, I'd do a positive pressure test on the unit to determine the condition of the seals and if there are any intrusion issues. Camping World dealers can all do a positive pressure test and you'll know if the unit is sound or if it's growing mold and rotting under the walls. You can also practice due diligence and nose around inside the unit, paying close attention to the front of the unit along the floor line, looking for evidence of water stains. Look at the curtains and blinds for staining as well. Open the cupboards close to the floor and inspect the transition between the walls and floor (behind the cabinets).
Look at the ceiling and look for any stains in the corners and feel the ceiling in various spots, especially along the edges where thew ceiling and walls meet. if it feels spongy, it's been leaking.
All RV's with the exception of very high end motorhomes like Newell and Prevost employ a synthetic material for the roof, underlaid with sheet luan and luan is wood and it rots.
In reality, it's not so much the rot thats bad (it's bad enough), it's the mold that comes with the rot. Some of that mold is toxic to breathe.
Be apprised, if it does show signs of water intrusion and a positive pressure test shows compromised seals and caulk, it can be a very expensive fix
You need to approach any older, used unit with open eyes and due diligence. Don't 'love' it until you know it's sound.