Another question, if I can deduct money for repairs, and I can depreciate the structure, does that mean I'm essentially double-dipping if I have to replace the roof? Theoretically I've been depreciating that every year, and then the year I replace it, it is one giant deductible expense?
Still not an expert, but:
When you spend money on your rental, you can either treat it as maintenance/repairs or improvements. Check the instructions for Schedule E, but generally maintenance and repairs are what they sound like (like paint, carpet, replacing a water heater). Improvements are things that would add value to the property (like a new garage or a new fence).
If you do maintenance or repairs, those are deducted as an expense on Schedule E in the year that you paid for them, and they reduce the rental income for that year. See line 14 of Schedule E. I would think that a roof replacement would fall under maintenance, although if you upgraded the shingles then you'd probably have to split the cost between maintenance and improvement.
If you do an improvement, then that adds to the basis of the property. You can depreciate the property every year on a given schedule - rentals appear to be a straight 27.5 schedule - so you would take the basis of the property and put depreciation of 1/27.5 of that amount every year on line 18 of Schedule E. If you make a capital improvement, then I'm not sure but I think you either have to depreciate that capital improvement on a separate schedule - I think you can find the answer to this question in IRS Pub 527.
In looking at a roof specifically, it may fall under Section 179, which means that you can depreciate it all in the first year of service, which essentially makes it like an expense in the current year rather than something that gets depreciated over several years. See instructions for Form 8962.
Do note that once you go to sell, that depreciation - whether you take it or not - does get subject to depreciation recapture - you essentially have to pay a tax on the total amount of depreciation once you sell it.
Finally, you'll also have to apparently split the value of the land and building and only depreciate the building on that 27.5 year schedule. Land doesn't depreciate.