Discussion on question by Timmy: What to do during summer to earn income? (tenured faculty)

I find the sentiment "I do not want to teach in Summer because there is no course in my area of specialty" to be extremely odd. I am a mathematician, a geometer/topologist. I routinely teach undergraduate classes in Calculus, Linear Algebra, Real Analysis, Complex Analysis..., whatever is needed. My attitude is that as a professional mathematician I should be able to teach any undergraduate class (some may require more preparation, some less).

I find it sad that someone for whom money is important (or at least important enough that $70K is not a sufficient yearly salary) didn't know that academia is a bad idea if money is important.