So, I decided to take the plunge, but holy smokes, no one told me how sturated the entire world is! I came in with the expectation that I would start at a smallish airport, but even most of them had at least 1 player. I was hard pressed to find an open airport that supported a good number of routes with a decent amount of demand (60 - 100 passengers) for this time period that wasn't already hogged.
When I did find such an airport, all of the possible routes were completely overrun by all the big, established airlines at the destinations. So, even if I started at a decent airport that no one is at, nearly every possible route had heavy competition. It took me a looong time (spent 2 hours just figuring where to start! [usually it takes me 5 minutes]) to find one that was ok.
Having said that, back on topic, I decided to go with used DC-7 initially because of its grand range (which I needed for the airport I started at) and its low lease cost. Having surveyed the new jetliner landscape, I think I will be going with Sud Aviation's beautiful Caravelle. It won't serve me on my longest routes, but it will take care of most of my needs. It will have lower operating costs, go faster, and have shorter turn-around than my DC-7s. All of that for around the same price, and don't have to wait in line!!