I need about $700,000. That’d cover state college for my kids, a new roof for our house and something for retirement. My daughter Sally, age 8, needs $7. That’s the difference between her life’s savings and the $15 price of a chunk of iron pyrite she wants to buy in the gem-and-rock shop downtown.

It’s nice to know someone whose financial goals are so attainable, and whose confidence will allow her, with eyes wide open, to invest everything she has in fool’s gold.

She gets $6 allowance each week, and a good report card is worth another $5 from Grandma. But Sally’s love of pretty stones gobbles up whatever she makes, and she’s always looking for more. Sally is full of ineffective money-making ideas.

Last month she offered 25-cent lessons to children who want to learn her trick of climbing up the inside of a doorway by bracing her limbs inside the jamb. She posted a sign on our street, but no students came forward to acquire this valuable skill.

Sally loves to sell things. A couple of years ago, when her big sister Marie had to move $50 worth of softball-league candy, Marie set up a table in front of our house.  Unfortunately, we live at the dead-end of a street in a neighborhood of 10 homes, isolated from the rest of town by a busy street and an idle factory. Marie made a sale to the mailman, but that was it.

So we enlisted Sally, then 6. I got a brown grocery bag, wrote the pertinent facts on it in big letters, cut holes for her arms and head, and stationed her outside the supermarket where she capered around and asked every shopper, “Would you like to buy some candy, madam?” (or “sir”) Marie stood off to the side, embarrassed by her goofy sister. But sales were brisk, and Sally learned the joy of selling.

 Not long afterward, she set up a table on the sidewalk in front of our house, hoping to sell her drawings. Sally sat there in such solitude that she might as well have been meditating at Walden Pond. A great place for a philosopher, but a lousy spot for an entrepreneur.

 When she had a yard sale, it had the same result. Location, location, location. On Halloween we could afford to give out two-pound boxes of imported chocolates because we get exactly five trick-or-treaters – not counting our three kids; that’s how many children live in this little backwater. The neighbor kids drifted down to Sally’s yard sale, but her offerings (used-up toys) tempted no one. She’d drilled another dry well.

In school Sally’s classmates are always asking her how to spell one word or another. The day she decided to charge 25 cents per word, Sally came home with 75 cents. But the next day her classmate Andrew announced he would spell any word free of charge, and all the kids flocked to him, though his credentials were dubious.

Sally stuck her nose in a book, but made sure all Andrew’s patrons heard her snickering at his spellings. Under his guidance, half the class wrote poems about Dr. MARTIAN Luther King Jr. in January, but they still preferred Andrew’s pro bono guesswork to Sally’s pricey expertise.

 Every so often, Sally makes some change folding laundry or shining my shoes. I don’t pay well, and she isn’t very capable. But like a die-hard prospector of the Old West, she never gives up her quest.

 And last weekend, she finally caught hold of something. We’d allowed Marie to have a little sleep-over party, with the usual proviso – that the big kids include Sally in their fun. Marie grudgingly agreed. 

Her sister’s visitors had barely arrived when Sally handed me four one-dollar bills, saying, “Put this in the Bank of Dad.” (I hold the kids’ savings and pay them 5 percent interest when I think of it, keeping track of everything in a notebook, paying them back whenever they want it.)

“Where’d you get this money?” I asked.

 “From Marie. She’s paying me to stay away from her and her friends.”

Marie has deep pockets ($143.94. I happen to know). Without realizing its commercial value, Sally herself has been an uncapped gusher of little-sister pestiness – black gold – a resource more abundant than Arabian oil. Eureka! Now with a way to make it pay, our little prospector has finally struck it rich.