My in-laws owned a vacation rental property in South Lake for a few years.
The biggest costs are not hidden: mortgage, property taxes, insurance.
In recent years insurers have dropped policies or jacked up premiums. Catastrophic fires forced them to reassess risk, especially urban areas near forests. This can be very expensive now, especially if you end up having to go with the insurer of last resort, the so-called FAIR plan.
Management fees: Depending on details of your plan, you may need a property manager. Figure about 8% off the top of rental income.
Heating: You'll have to heat the house during winter even when unoccupied or the pipes will freeze. Cost depends on size and efficiency of house.
You may need to pay for someone to clear snow from your driveway/road. Actual cost depends on who owns the road and if you're willing/able to clear you own driveway (clearing "Sierra Cement" weeks or even days after it falls and compresses is no fun).
Assuming there's landscaping, you'll need to winterize the yard every fall and then get it ready again in the spring.
More generally, the amount and duration of snow is hard on structures, so be prepared for increased maintenance costs.
If they rented it very aggressively, and during the peak season, then they'd almost break even. But then they couldn't use it when they wanted to. Seemed pointless to lose money on a property they couldn't really enjoy, so they sold.