Yes, you can deduct 100% of the repairs or improvements that are specifically for rental purposes with no personal use. Improvements such as the porch are subject to depreciation and must be listed as an asset using the same 27.5 year recovery for residential rental.
The swamp cooler that is not used by the tenants at all should not be deducted as part of the rental. Any improvements to the entire garage or to the entire property that does include the rental can be depreciated at the 21% rate.
