Canada makes it a bit more clear. Do you expect to ever pay taxes on the income? If not then its not taxable, you can't claim just for deductions.
There has to be an expectation of profit, on top of the FMV. It doesn't mean you have to profit, it should be expected that you would under reasonable circumstances. Its to prevent fraud where people claim room mates or tenants just for tax deductions, eventually its expected that the extra income will exceed expenses. I would expect the US to be similar, uncle Sam isn't exactly generous and doesn't really want to send you a refund.
Since Mezzie is only writing off repairs its presumed that next year there should be profit, or the year after, eventually repairs are over with and then there will be taxes owed on the income.