BOSTON (CBS) – I have been talking all this week about the website The Simple Dollar and the founder Trent Hamm. We have more of his simple rules today. I am intrigued by the next two rules.

Know how much money you actually take home per hour you devote to work. Figure out how much you earned last year after taxes, then subtract from that all of the costs of commuting, professional clothes, work-related meals, and other expenses you paid out of pocket.

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Then figure out how many hours you worked (including those at home), plus the hours you commuted and attended other business meetings. Divide your after-expenses income by your total hours work to get your true hourly wage. That’s how much you actually sell an hour of your time for.

Interesting theory. Someone earning $50,000 with a commute could be earning $12 an hour after taxes and expenses.

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Use your true hourly wage as a comparison point for everything you buy. Your true hourly wage is an incredibly valuable number. Let’s say your “true wage” is $10 per hour. If you’re looking at buying a $20 Blu-ray, is that worth two hours of your life when you could just rent it or borrow it from the library?

What about a $1,000 television? Is it worth 100 hours of your life to have that particular model when you could have a less expensive model instead?

I would think if we all began to put an hourly price tag on what we purchase there would be far less frivolous purchases. It’s almost as good as asking yourself, “Do I need it or do I want it?”

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Buy cars based on reliability and fuel efficiency. Those are the two factors you should think about above all else when it comes to buying a car because they will make an enormous difference in your finances. A reliable and fuel-efficient car will keep your fuel bills and your repair bills low for the entire time that you own it. You can research reliability at your local library by taking a look at reliability data from Consumer Reports; fuel efficiency is easy to find at websites like