Also, in case it makes a difference, we have 2 other properties but only selected one of the 3 to use section 179 for. 

Are "services" (such as maid service or meals) provided?

If not, it belongs on Schedule  E, not Schedule C.  If it is on Schedule E, 27.5 years is correct (assuming it is in the US).  However, Section 179 would not be allowed on the building itself.

If "services" are provided, then Schedule C is correct, but you need to use 39 years (assuming it is in the US).  But Section 179 would only be allowed for a roof, furnace/ac, fire system/alarm and security system.  Section 179 would not be allowed on the rest of it.