I'll sum it up in two words: Just don't.
In the early 90's a good rule of thumb was to pay 5 times annual cash flow for a broadcast property, based on the previous five years. Nowadays it would be more prudent to base that on projected cash flow for the next five.
If I had the money and the burning desire to own a station, I'd only buy one with a city grade signal over the entire market, and pay only as much as the real estate and equipment are worth.
It would also be a good idea to have enough capital in reserve to operate the property for a year (or two) with no revenue.
Beyond that, I'd look for a good 'Brand' that could be leveraged across other media.
Financially, you might be better off investing in mint-condition Pokemon cards.