The phrase "second career" takes on a new meaning when listening to Charles Givens extoll, promote and advise the public on taking its financial affairs into its own hands.

At 44, he's the co-owner of the U.S. Football League's Orlando Renegades (formerly the Washington Federals), the owner of 37 real estate holding firms, a modeling studio, a television production company, a printing plant, a dinner theater and a leasing company. He made his first million dollars at age 25 and went broke the first time, he says, at 26. Since then, he claims to have made and lost fortunes eight times. He estimates his current assets at more than $50 million.

Nine years ago he founded the Charles J. Givens Foundation, a nonprofit corporation headquartered in Altamonte Springs, Fla., to teach middle-income people "Money Strategies" -- the name of his financial how-to seminars that have him on the road 42 weeks a year. His message: As your second career, become your own financial manager.

"In the '80s, you have got to become your own money manager," says Givens in his evangelistic style, emphasizing certain phrases as he has done hundreds of times before in his free introductory seminars. "No one will ever watch your money as well as you will -- no financial planner, no broker, no banker.

"Making money is not a matter of finding a get-rich-quick scheme. It's not a matter of hiring high-priced tax help or high-priced investment help, which most people can't afford anyway. It's a matter of do-it-yourself, do-it-at-home, do-it-in-your-spare-time strategies."

Givens doesn't hesitate to pinpoint what his money strategies will achieve for people who apply them. He says matter-of-factly: "They reduce your taxes by 50 percent within one or two years, and that would save thousands of dollars. Secondly, you'll double your investment money every 3 1/2 years.

"Even if someone does nothing more than follow my advice on taxes and invests 10 percent out of every paycheck, they'll probably double the income they're now getting from their job within a few years."

Beyond the cost of his educational package (making money isn't cheap -- the video package is $325, and the audio $295; both include a workshop and two-day money conference), Givens says wealth requires time, not big bucks. He claims two hours a week will gradually turn your financial life around -- one hour to read, to learn about money and to follow the changes in the tax laws, and another hour to apply the strategies.

Among Givens' "succinct and simple" tips, from taxes to investment to borrowing money, to help you "work smarter instead of harder":

*"Job 1 for all Americans is to use tax laws in their favor," Givens says, disavowing tax protests, cheating and loopholes. "The first strategy is to make what you already spend money on tax deductible." For example, Givens says there are seven ways in the tax code that allow you to turn vacation expenses into a tax deduction. One way: If, while traveling, you go on a job interview (same type of career or position) or if you attend educational programs relating to your job, to taxes or investing, you can take a deduction on part or all of the costs of your trip.

*Starting a small business, says Givens, is one of the best tax breaks. "You can run it from your home, part-time. Become a consultant. Everyone is good at something." If you use your automobile 50 percent of the time for that business, you may deduct, the first year, up to $4,000 of its cost. Same thing is true of your videotape recorder, your home computer and other equipment, he says.

*Hire your children or grandchildren to work for the home business. "Instead of paying your kids allowances," says Givens, "hire your kids to clean the business office, wash the business car, stuff envelopes. The money you would've given them anyway adds up to a $2,000 tax deduction. The tax code says you don't have to withhold any taxes on family members, and you don't have to pay Social Security or federal unemployment."

*Take out an asset management account instead of a checking account. "They're a substitute for your checking account . . . but you can earn up to 11 percent," he says. "Consolidated Asset Management in Valley Forge, Pa., offers one with no minimum deposit, no minimum balance, and it's paying right now a little less than 8 percent guaranteed interest -- twice what any bank will give you on unlimited checking. An added quirk: It takes five to 10 days to process their checks so you're earning interest on money you've already spent."

*Invest in no-load mutual funds and reposition your investment between stock funds, bond funds and money-market funds, depending on what interest rates are doing. "When interest rates are low, put your money in stocks," he says. "When interest rates are high but coming down, put your money in bonds. When they're low and going up or high and going up, put it in money market."

*Other People's Money (OPM, Givens calls it) -- "America was built on other people's money." He says credit has three uses: to go out and buy things that perish, such as dinners and gasoline (the worst use); to buy things that will last the life of the payments, such as paying three years for furniture that will last five years (a better use); and the best use -- borrow money at one interest rate for something like a home that will appreciate on your initial investment 50 to 100 percent. Buying a home to live in should be top priority, he says. Office Paychecks

Office employes are averaging $283 weekly, up from $270 in 1984, according to the Administrative Management Society's 1985-86 Office Salaries Directory, a survey of salary and benefit information of 20 clerical, secretarial, administrative and word processing positions. The lowest-paid office workers were file clerks -- who would spend half their weekly salary to purchase the $115 directory, available from the society's main office at 2360 Maryland Rd., Willow Grove, Pa. 19090.