Residential rental properties get depreciated straight line over a 27-1/2 year period, and they are subject to the mid-month convention, which means they are treated as placed in service on the 15th daqy of the month. So you would get 1-1/2 months worth of depreciation for 2012. That means you get 1.5/330 = 0.454545% of the basis in the building for depreciation (some of the purchase price should be allocated to the land which is not depreciable).
Let's assume you allocate $40,000 of purchase price to land. You have $155,000 of depreciable basis in the building. $155,000 x 0.454545 = $705 of depreciation.