NEW YORK (CNN/Money) - In a time when mortgages, car payments and student loans are as much American as baseball and fast food, Steven and Erica Ploof seem like throwbacks from their grandparents' generation.

Other than their mortgage, which is more than 50 percent paid off, the Sterling, Mass. couple have no debt to speak of. When they want to buy something, be it a car or airline tickets, they save and pay in full. "If you don't owe anything, you don't need much money," said Steven, 31, who thanks his father for his financial philosophy.

Steven graduated from high school with $4,000 in the bank. Then, by working as a live-in counselor at a home for mentally ill adults, he finished college with no debt and a $10,000 cash cushion.

Today Steven is a certified public accountant for a manufacturing company, a career he chose not for a love of numbers but because he wanted a four-year degree in a field that paid well. Erica, 34, who is also an accountant, dedicates most of her time to the couple's children, Conner, 4, and Jack, 2, but does some consulting work throughout the year.

With a nest egg worth more than $340,000 - not including the $200,000 equity in their home - and an aggressive savings plan, the Ploofs are well on their way to millionaire status. Based on their current savings rate, they'll hit that mark in less than nine years, assuming a 9 percent rate of return. But that's not their goal.

"Even though I talk about saving all of the time, I have no interest in being rich," said Steven. What he wants is to retire from his job as an accountant by the time he's 40 or 45, spend more time with Erica, Jack and Conner, who is autistic, and work with other children with autism. "I want to build a good foundation and do what I really want to do," he said.

When it comes to investing, Steven and Erica do it all by the book. That is, they first take advantage of every tax-break they can get. Steven makes the maximum contribution allowed to his company 401(k) while Erica gives her simplified employee pension plan (SEPP) first dibs on her consulting income. They further boost their after-tax savings by socking away money in Education IRAs for each of the boys.

After they save in their retirement accounts, the Ploofs typically take home about $4,000 a month. Of that, they automatically invest $600 a month in three Vanguard funds - an index fund, an aggressive growth fund and a balanced fund - making weekly contributions for the purpose of dollar cost averaging.

When their income is higher than usual, which happens when Erica works more or Steven's profit-sharing plan does well, the couple add the windfall to their Vanguard account, their cash holdings or a portfolio of individual stock. Right now they own Johnson & Johnson (JNJ: Research, Estimates), which they consider a long-term holding, and EMC (EMC: Research, Estimates) and Parametric Technology (PMTC: Research, Estimates), local companies they felt were undervalued.

The final, and perhaps most important, aspect of the Ploof's savings strategy is paying an extra $400 every month toward their mortgage. In doing so, they'll own their house outright in nine years, about when Steve turns 40. At that point they'll have zero debt and, hopefully, enough saved to make early retirement a reality.