I can tell you that the Police RK is a cheap alternative to enter the realm of the Road King. The newer models have the 103" engine, 6 speed tranny, factory tach and are ABS equipped. They are usually bought for about $12-13k. Now, to make it look less "official", you'll have to put some coin into it, but if you don't mind wrenching a bike, then you'll be ok. As far as any maintenance concerns, about the only thing I'd say you may want to check for is clutch problems. Cops are hard on clutches. PD bikes are meticulously maintained though and rarely ever abused (cops love their scoots). PD lease turn-ins are only (usually) in service for two years and as part of the H-D lease agreement, have to be serviced by a certified H-D tech. Now, you won't get the extra shiney stuff with a PD bike, probably not cruise control, either...but if that stuff is of little importance to you...I'd say your on the right track.
Either way, let us know how it works out for you.
JD