I don't consider myself an expert by any stretch of the imagination but I'll share some experience sprinkled with a bit of opinion.
Department store bikes are garbage. EVERY time we have a group ride with someone on one, there's usually a problem, if not on the ride, shortly after. Dried/gummed up/grinding bottom brackets, loose headsets, cross threaded pedals, improperly adjusted brakes, rusty hardware, misaligned derailleurs, out of true wheels/loose spokes, dry chains and not fit to the person at all.
As soon as the person goes and buys a well-built bicycle they are so much happier. When they get the bike fit performed, it's like a revelation for them.
In all honesty, you can get a left-over year model or a base model bike from a LBS (local bike shop) close to what you'd pay for a department store bike.
The insight you gain from the LBS will be invaluable. The profit margins on new bike sales are razor thin, most of the profit is made up in accessories and repairs. The LBS usually depends on word of mouth to get customers into their store, they usually won't misdirect a customer because the damage it can do to their business would be vast. Granted, not every LBS employee is respectful of new cyclists or recreational riders. There's one LBS by me that hires enthusiasts for mountain biking, road cycling is considered "lame" by them. Again, I won't go their because they have a prejudicial view of what the "ideal" customer should be. The shop we frequented before moving catered to all cyclists, had 3 different types of fitting performed, and gave unlimited adjustments for the first year. the LBS we frequent now carries a much smaller product line, but offers the same level of service. A good LBS will answer any question you have at any time, because of this, please give them your busines rather than one of the internet giants.
As stated previously, Craigslist/ebay can be a treasure trove of stuff if you know what you're looking for. I steer clear of them, been ripped off one too many times. Unfortunately, the wisdom only comes with experience and education.