$1000 for a new, 20hp four stroke outboard does not sound right. Thats about the price of a two stroke 9.9 kicker. The $4900 sounds about right considering what that motor should sell for. New boat prices are out of sight. I have a 20 foot deep V aluminum boat I bought back in 1987, complete with 60hp Merc and trailer for $8700 new. The same rig now is about $18,000 new. Set Up usually includes mounting the motor, fitting the trailer, a gas can and line, battery, and usually a coast guard kit (life preservers, a throwable, fire extinguisher, signal device, anchor).
I have spent a lot of time on lake Ontario trolling for trout and salmon in a 16 foot tin boat, sometimes in some pretty bad weather. Tin boats are like beer cans, they tend to float high in the water. But, as was posted earlier, high gunwales are important for rough weather. There are "big" 16 footers, and "small" 16 footers. You would be amazed what a boat can handle if the operator knows what he is doing.
A boat like you describe should be fine for most inland lakes. The semi V will help with the chop. Just use common sense, and invest in a cheap hand held Marine Radio for safety and weather updates / warnings.
Larry