What do they do for a living???
They earned their money the old fashioned way ... they inherit it! 
More likely, they were in the right place at the right time .....
But, what about the 'average' guy? I'm still in awe of how much disposable income is out there. How do most shorefront vacation home owners swing two houses, pay taxes, own a $75,000 boat, and send the kids to college? Where is all this money coming from? The typical lakefront property probably has a current market price of $550,000 .... the 'average Joe' (myself included) can not possibly comprehend how much cash is summering on Lake Winnipesaukee.
Perhaps some of these folks have inherited the property? Are they financed up to their eyeballs? Are they all doctors & plumbers? Or lawyers & real estate agents? Are their kids not going to college? Just curious ....
Interestingly, I've heard (multiple times) that when Mom & Dad leave their Winnipesaukee house (with the best of intent), to their children, it inevitably is liquidated & proceeds divided because of conflicts between siblings and/or their spouses. With this in mind, I don't believe that many of these properties are inherited by 'average Joe'.