With today's department store bike, there are two issues; what's in the box, and who puts it together. A good mechanic should be able to make a reasonably reliable bike out of what comes out of the box, though s/he probably won't enjoy the process. A lot of work may be involved, tensioning the spokes, greasing and adjusting every moving part, and so on. If you do that work yourself, it's probably worth the time. A bike shop may do it for you, but they will not be cheap.