I believe that the shower in the second floor bathroom is causing water damage and creating the mold in the first floor bathroom ceiling, which may require removing the first floor bathroom ceiling. 

In that same 6 years I have had to replace the stove and water heater, have the dryer and oven fixed, and had a tree trimmed and an eve repaired.

Consider putting in a separate electrical meter, a separate water meter, and separate gas meter.

Also study costs of roof replacements, furnaces and water heaters.

She didn't think the case holds much water but it could be very time consuming resulting in high fees.

Try and also have it close to the rear or front garden hose spicket.If the renter(s) are going to use a small unstable grill or "Cheap" grill it might be a good idea to ban it or require the above.

The water is always cold, but at least in the summer it is nice outside of the water and the winter air temps are probably higher than the Tahoe winter air temps. 

Without knowing more about the location though, if this cabin has direct water views and is able to sleep at least 6 people, a fully renovated version of your cabin could probably pull in at least $600/night in the summer without much effort. 

Plus its a non stop location for tourism Summer Camping, White Water Rafting, Rock climbing, 4 Wheeler/ATV, Hunting, Fishing.Winter - Ski, Snowboard, Tube, Ice Fishing, Hunting, Winter Breaks away from the Heat etc.

The reason I ask if it used to ascertain damage to something on the lot (water/sewer/utilities hookups or something) and you don't have pics and mutually signed documentation from the lessor/lessee upon each tenant's move in prior to your ownership, would you be able to justify a charge upon move out?