If you were not depreciating it, I recommend going to a tax professional to fix it (with Form 3115).
If the Fair Market Value when you started to rent it was LESS that your Cost, the deductible "loss" is based on the Fair Market Value, not the Cost. TurboTax does NOT guide you correctly for that scenario, so you consider a tax professional, or post back when you are filing the tax return for help for how to report it on your tax return.
