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SPECIAL LOW 5.9% INTRODUCTORY RATE!... First-year 4% bonus!... Act now! You're increasingly hearing those kinds of come-ons for credit products like home-equity loans and savings vehicles like annuities. Banks and other financial firms are so anxious to get your business, they'll promise you the moon--or at least an interest rate that sounds too good to be true--to get you in the door.

Problem is, those teaser rates usually last for a year or less before zooming up (or down), often to levels substantially worse than you could find by shopping around. So only suckers take the bait, right? Not necessarily. You can turn some of these deals to your advantage, at least for the short run. Here's how to identify the opportunities among six financial products that commonly carry teasers:

Credit cards. Nearly two-thirds of the more than 2 billion credit-card solicitations mailed each year trumpet low introductory rates, according to the Tarrytown, N.Y. card tracking firm Behavioral Analysis. Those rates range from 4.9% to 12.9% and typically last six to 12 months before jumping to 17% or 18%, on average. Such rates are almost 10 percentage points above the best cards available (see the table at the bottom of the following page).

If you carry a balance on a high-rate card but intend to pay it down, transferring that balance to a card with a low teaser rate makes sense. Paying, say, 5.9% instead of 15.9% on a typical $1,800 card balance will save you $180 in interest for the first year. Once you've pared the balance to zero, it won't matter to you what the card's rate is. If you haven't paid off your balance by the time the teaser expires, simply shift it to another teaser-rate card and cancel the previous one. (Caveat: If you have poor credit, you may not qualify for these cards.) One of the best teaser cards recently: First USA Visa or MasterCard (rate: 5.9% for the first six months, then a below-average 13.99%; no fee; 800-347-7887).

Home-equity lines of credit. About 25% of home-equity lenders now offer introductory interest rates on home-equity lines of credit (HELs), according to mortgage trackers HSH Associates, up from 19% just six months ago. The average HEL rate stands about 1.5 points above prime, or 10.22% recently. But the teasers are often equal to or even one point below prime, usually for six months to a year; the lowest we've seen recently was 4.5% for the first three months from Sovereign Bank in Bethlehem, Pa. After that, it jumps to prime plus 1.5 points. But post-tease rates on some HELs leap higher, to levels above those prevailing in their local markets.

"It's unlikely you'll be able to pay back a home-equity line during the introductory period," cautions Keith Gumbinger, vice president at HSH Associates. If you expect to use the credit line for more than, say, three years, you're better off comparison shopping based on the post-teaser rate.

Adjustable-rate mortgages. About a third of ARMs come with ultralow introductory (usually one-year) interest rates of, say, 4.2%, vs. the recent average rate of 5.78%. If you want an ARM--which can be a better deal than a fixed-rate loan if you plan on staying in your home for less than six years--such a teaser rate can really save you money. That's because all ARMs have caps on how much your rate can go up in a given year (typically two percentage points) and over the life of the loan (six percentage points). A low initial rate will stay lower than average in future years as interest rates change.

One drawback: ARMs with teaser rates virtually never waive points, those initial fees that can run as high as 3% of the value of the loan; about 25% of non-teaser-rate ARMs do. To figure out whether a teaser-rate or regular ARM is a better deal, ask lenders to calculate the total cost of each loan--the interest over the expected life of the loan plus points.

Money-market funds. A whopping 57% of all money funds--including all the top yielders in the table at right--offer their own version of a teaser rate by waiving all or part of their management expenses, according to IBC's Money Fund Report. That has the effect of boosting your yield by about half a percentage point, to 5.9% or so for the top taxable funds.

Fee waivers aren't necessarily permanent, though. Fund companies can reinstate expenses at any time. To increase your chances of finding one that won't pull the plug after you've poured in your cash, stick with large fund families like Dreyfus and Vanguard that have waived fees a year or more, says Ralph Norton, editor of IBC's Money Fund Report. They're less likely to reinstate the fees because they use money funds as loss leaders, hoping you'll eventually switch at least some cash to their more profitable stock and bond funds.

Certificates of deposit. A callable CD offers a higher-than-average rate but gives the bank the chance to cancel the CD after a stated time period--usually six months to a year on a five-year CD. For example, Charter One Bank in Cleveland recently offered a five-year CD that's callable after a year and pays a 6.6% yield. That's 0.18 percentage points higher than the rate on the nation's best noncallable five-year CD (see the table at top, right).

Bank on it, though: If rates fall while your CD can be called, it will be, forcing you to reinvest at the lower, prevailing rates. So choose a callable CD only if you think rates will stay flat or rise slightly during the entire life of the CD.

Fixed annuities. These tax-advantaged savings vehicles, issued by insurance companies, recently paid an average of 5.8% ("fixed" refers to the principal, which is guaranteed by the issuer; the rate changes, usually once a year). An estimated 25% to 30% of these annuities, including ones from Lincoln Benefit Life and Jackson National, offer a so-called bonus rate for the first year of one to four percentage points over the normal interest rate.

In general, though, teaser-rate annuities are a bad deal. You have no guarantee that a high first-year bonus will mean high returns over the long term. That's because insurance companies usually don't peg their rates to a benchmark, such as the one-year Treasury yield, but set rates based in part on how their investment portfolios have performed. If post-tease payouts fall below average, you're out of luck: Surrender charges can run as high as 10% over the first 10 years, and withdrawals you make before age 59è are subject to a 10% tax penalty. That makes for one teaser you'd do well to resist.