The nation's go-to housing finance program for the last few years is about to become more expensive. Or is it?

Beginning Monday there will be changes in the way borrowers pay for the privilege of using low-down-payment, government-insured mortgages to buy or refinance a house. An analysis shows that, although the monthly premium will rise 64%, the overall cost will fall — at least in the short term.

That's because the Federal Housing Administration also is trimming its upfront premium, to 1% of the loan amount from 2.25%. And the net result for most people will be lower monthly payments for the first few years their loans are on the books.

First, here are a few basics: The FHA doesn't make mortgages; rather, it insures them. The insurance takes the place of the 20% down payment that lenders would otherwise require. If the borrower fails to make payments as promised, the insurance steps in to make the lender whole.

FHA-insured loans are practically the only low-down-payment game in town. As such, the FHA's share of the mortgage market has gone from an all-time low of about 3% just a few years ago, when the housing market was going gangbusters, to 30%-plus today. Some estimates put the FHA's market share at almost 50%.

By either count, the powers that be in Washington have decided that's too big a piece of the pie for a program that was originally intended to serve just those who cannot obtain financing anywhere else.

Moreover, because most of the FHA-insured mortgages written today are made to borrowers with just a minimal 3.5% cash outlay from their own pockets, the default rate is higher than it has ever been. As a result, the agency's capital reserve account has fallen below the level mandated by Congress.

Thus, the government had to decide how to maintain the viability of the FHA's mutual mortgage insurance fund while continuing to support the housing market during this time of need. So here is what it's doing.

On new low-down-payment FHA-insured loans originated on or after Oct. 4, the annual premium will rise to 0.9% of the loan amount from 0.55%. At the same time, though, the upfront premium will be lowered to 1% of the loan amount from 2.25%.

And because most borrowers choose to finance the initial fee as part of the loan amount, the overall effect will be easier on the checkbook — for a few years, anyway.

Using number crunching from Zillow Mortgage Marketplace, let's look at an example of a $200,000 house being purchased with 3.5% down.

Currently, the 2.25% upfront premium on a $193,000 mortgage would cost about $4,343, and the 0.55% annual premium would be about $1,062 — or $88.50 a month. But starting Monday, that all changes.

Under the new fee structure, the upfront premium drops to 1% of the loan amount, or $1,930, while the annual premium jumps to 0.9%, which is $1,737, or $144.75 a month.

For borrowers with enough money to pay the upfront fee at closing, the changes mean about $2,413 less cash to close but a monthly payment that is about $56 higher.

But remember, these are mostly low-down-payment mortgages made to people with not a lot of cash on hand. Most FHA borrowers roll the initial fee into the loan amount. And if you do that, the bottom line is that your payments will be lower for the first few years of the mortgage.

The numbers may come out differently depending on the loan amount — and the FHA currently backs loans up to $729,250 in high-cost markets. But here's how they play out with the $193,000 mortgage above.

In the first year, according to Zillow, the payout for mortgage insurance will be $3,667 under the new premium schedule, as opposed to $5,404 under the old one. In the second year, the cumulative mortgage insurance payout will be $5,404 versus $6,465.50. And in the third, the cumulative payout will be $7,141 versus $7,527.

It isn't until the fourth year of this loan that the FHA-insured mortgage becomes more expensive under the new fee structure. Then the cumulative cost will be $8,878, as opposed to $8,588.50 under the old schedule.

Of course, most borrowers keep their mortgages for more than four years. And at today's super-low rates, it's hard to see how there would be much of an incentive to refinance — unless it is to get out of paying for FHA insurance.

Consequently, private companies that offer lenders the same coverage as the government can be expected to mount campaigns to wrestle business away from Uncle Sam on the basis of cost.

Recently, private-mortgage insurers like Radian, MGIC, PMI and United Guaranty have been largely out of the marketplace, licking their wounds from the huge number of bad loans they backed. But the FHA welcomes the competition.

FHA officials would be happy if the agency's market share fell back to a more reasonable percentage, say, 12% to 18%. But their real fear is that private insurers will "skim off" the most creditworthy low-down-payment borrowers, leaving the government with the most risky. If that happens, it's a good bet that Uncle Sam will have to raise the ante once again.