Ever since I first read about fellow Fool Matt Richey's deep value investing play, Imperial Parking (AMEX:IPK), I have been intrigued by the concept of buying a parking lot company. It just makes so much sense. Everybody who drives has to park somewhere. There are only a limited number of places in which to park -- especially at sporting arenas, universities, airports, and, of course, in cities in general. If a company owns a large chunk of the places in which people want to put their cars and charges them cash money for the privilege, it pretty much has a captive audience and a secure revenue stream from here to eternity.

That is, unless and until sales of Segway scooters pick up on Amazon.com (NASDAQ:AMZN).

Now I have to admit that the story of what ultimately happened with Impark, as the company is known, how it was scooped up at a bargain price in a leveraged buyout by the Gates Group with financing provided by Prudential (NYSE:PRU), got me a little down. Not least because I had bought shares in Impark myself and was on the receiving end of the bargain price.

Still, I love the economic model of the parking business. So when Central Parking (NYSE:CPC) put out its earnings release last week, I read it right away and was intrigued. Then I examined its free cash flow situation and was dismayed.

Here are the details. In its fiscal third quarter of 2004, Central reversed its year-ago earnings loss to rake in $0.16 per diluted share, despite growing revenues just 3.4%. Over the long term, too, the picture is improving. For its first nine months of fiscal 2003, Central also recorded a loss. But this year that reversed. The company is in the black by $0.49 per diluted share so far and looks on target to make about $0.65 for the year, for a forward P/E of about 25.

Now the bad news. Whereas Impark also generally had a P/E in the mid-20s, its accounting never really reflected the real cash-cow nature of the business. When Matt first wrote about it, Impark's enterprise value-to-free cash flow ratio was just 8. That's not at all the case with Central. Despite the past quarter having been uncharacteristically free cash flow positive for the company, by my calculations, Central still has an EV/FCF of 46 -- very high. So while in theory I would love to park some investing money in Central, at its current price, I'd rather walk.

Fool contributor Rich Smith has no interest in any of the companies mentioned in this article.