To a first-time homebuyer, which I was not long ago, what possible difference could a minuscule sounding half or three-quarters a percentage point or so make?

Half a percent? Three-quarters? Whoop-ti-do, right? I mean, that's far less than the margin of error for most polls. Half a percent -- just 50 little basis points. P-shaw

Then we started the buying process. Time for the real world of finance to slap us in the face like a cold, dead salmon. Cumulative interest and principal and basis points -- not the kind of language a career in journalism prepares you for.

Very quickly we learned that half a percentage point can make or break a deal for some, or at least make a big difference in your home buying decision.

Let's say you're buying a $125,000 house, paying a standard $2,000 a year in property taxes for lousy public schools and $600 a year in homeowners insurance you probably won't use unless you decide to torch the place and relocate to Fiji. (Bear with me, I'm trying to make this interesting -- this is where most folks' eyes glaze over like they're listening to Dick Cavett recite the Federal Register.)

So -- a $125,000 loan, and you've chosen a 30-year fixed rate mortgage. At 6.5 percent, your monthly note including taxes, insurance and mortgage insurance is $1,076.

Bump that up half a percentage point and you're paying $1,118. At a 7.5 percent rate, you're talking $1,160. And God forbid it goes this high, but at 8 percent -- just 1.5 percent above where we started, your monthly would be $1,203.

Now, for some, a difference of between about $30 and $130 a month is no big deal. For my wife and myself, it was a key factor (we locked in low and paid for a few points) in whether or not to get an outdoor spa.

For others still, $100 a month is indeed a deal breaker.

And for that minority of you who take the longer view beyond "What's my monthly?", that difference in the interest you pay over the life of the loan is staggering. If you lock in at 8 percent instead of 6.5 percent, you will pay $45,764 more for your home!

If you lock in at 7 percent instead of 6.5 percent, that little half a percentage point will cost you $14,956.

If you have that kind of money to throw away, by all means e-mail me -- I have some great investment ideas.

Now, there is no magic trick or exact science to picking the right time to lock that rate in, but there are some basic indicators to look for. Watch the yields on the 30-year Treasury notes. Your local paper probably carries them boxed on the front page of the business section. We at Real Times carry them updated every day. (Hint hint)

Thirty-year mortgage rates generally track along with the yield on benchmark 30-year Treasuries. They start climbing for several days in a row, I'll bet you anything mortgage rates follow. Also, unusual volatility (which means it goes up and down a lot and erratically for a few days) can be a harbinger of climbing rates.

The stock and bond markets wigged out last week at comments Fed Chairman Alan Greenspan made. Granted, market analysts try to divine more from Greenspan scratching his behind than a primitive shaman does from chicken entrails, but it was a classic scenario.

Greenspan worries aloud the economy could get too hot, and in that case, he says, raising the rate that banks set to loan each other money wouldn't be a bad idea. The bond market went a-tumbling and yields skyrocketed.

Almost like clockwork. And viola, within a week rates had climbed 50 basis points. Half a percent.

That's right, dear heart. No outdoor spa this year.