A new five-year, $2 billion program announced this week by Fannie Mae, the federally chartered mortgage lender, will help some 20,000 low and middle-income Maine families realize the American dream of homeownership. If they can find a place to make the dream come true.

It’s a big if. As the nation’s largest source of financing for home mortgages opens the door, an increasing number of Maine communities are raising the drawbridge. Limits on building permits are for now a southern Maine phenomena, but one in danger of spreading.

A trickle of towns in coastal York and Cumberland counties have enacted permit caps recently, but a state Supreme Court ruling last month upholding Eliot’s 22-year-old growth-control ordinance has opened the floodgate. North Yarmouth cut its annual number of permits from 55 to 30, Cumberland is considering a cap of 44, York votes later this on summer on 84 (a reduction by nearly half), Falmouth is looking at 100. In Scarborough, mere talk about a cap sparked a run on building permits.

It’s being done to curb sprawl, and a more parochial and short-sighted way to do it would be difficult to conceive. The parochial part is that caps merely shove the costs of sprawl into the neighboring town, which enacts caps and shoves it further along. The short-sighted part is that the communities imposing these caps are the very same communities crying for workers to staff their low and middle-income jobs. Low wages and a long commute simply are not compatible.

Unlike other states, Maine’s sprawl is not the result of population growth, but of population shift — as building downtown becomes ever more difficult, as litigious abutters raise ever more arcane objections, those who want to build find it much easier, even necessary, to move to the edge of town. Therein lies the opportunity for Fannie Mae’s House Northern New England program to help solve several problems at once.

In every village and urban center, it’s not hard to find vacant buildings — storefronts, apartments, modest homes. Fannie Mae and the Maine State Housing Authority have the financial resources and the expertise needed to revive these properties. There are thousands of working Maine families that need these properties. What remains is for civic leaders to lead.

A good first step would be for every community concerned about sprawl to take an inventory of unused or underused buildings in the municipal center. Local zoning ordinances should be examined to identify those sections and clauses most open to conflicting interpretations and the conflicts must be corrected — the purpose of ordinances, after all, is to make the rules clear, not to generate lawsuits. Finally, those who worry about labor shortages and those who see permit caps as the way to control municipal costs and to keep the countryside from getting gobbled up must realize that the answer is not forcing people out, but drawing them in.