In the tiny, working-class Prince George's County suburb of Mount Rainier, economic prosperity is measured in parking meters: Each new meter along Rhode Island Avenue is welcomed as a sign of more business for the town's shops.

Five miles away in Capitol Heights, officials stand ready with local tax breaks and federal community development block grants, seeking to lure hesitant developers to a fledgling enterprise zone and to rid Central Avenue of vacant buildings. With a long-stalled town house project now under way, the town's population is expected to double to 8,000 in two years.

The meters, money, tax breaks and boosterism are signs that an economic development boom, which already has poured billions of dollars into outer areas of Prince George's, is starting to spread to older communities inside the Capital Beltway.

"There are, in our opinion, some tremendous opportunities in the inner Beltway that people haven't realized," said Gary W. Michael, vice president of a Riverdale development company.

"It is all part of the image of the county, the reality of the county," said Tim Ayers, spokesman for County Executive Parris Glendening. "We aren't going to have new, more distant development if the core of the county is left to deteriorate."

"The last thing we want is two Prince George's counties," said Lynda Given, director of the Prince George's Housing and Community Development Department. Since 1985, the department has spent $8.6 million in community development block grant funds on improvements and economic development in the inner Beltway area.

Attracted by 1,000 acres of undeveloped county land inside the Beltway, developers are taking a second look at some of the county's older, poorer communities. Many run-down structures have been rehabilitated. Housing subdivisions are springing up, and developers are razing some old buildings to clear the way for new commercial and retail centers.

"As the county succeeds more, which is definitely in the works with this renaissance of economic development, the attractiveness of those communities will increase, particularly the ones with advantages of having Metro and highway access," said Jay Langford, a planning official for the Metropolitan Washington Council of Governments.

For years, the inner Beltway communities have helped tarnish the county's image. Shopping strips along highways leading from the District to the county have fallen into disrepair. Low-income garden apartments, hastily built 20 years ago to accommodate a suburban population explosion, have deteriorated. Years of marginal growth and a tax freeze approved by voters in 1978 strained county and municipal services. Crime increased and developers stayed away.

In recent years, an economic renaissance has taken hold in Prince George's, transforming the county into one of the hottest markets in the Washington area. Influenced by relatively low land prices, a sound road network, proximity to the District and the pro-growth sentiment of county officials, developers have flocked to the county.

But the explosive growth has occurred primarily outside the Beltway: in Laurel at the county's northern outskirts, in Bowie at the county's eastern edge, in the Capital Centre area at Landover just outside the Beltway, in nearby Largo and at Tantallon in the south.

Just outside the Beltway in Greenbelt, tall, smoked-glass office buildings, trendy shopping centers and custom-built homes are helping to shape the county's revised image. New projects elsewhere include the planned $1 billion PortAmerica mixed-use development on the Potomac River, the $400 million Bowie New Town Center and $750 million Presidential Corporate Center. New housing, still cheaper than homes in Montgomery County and Northern Virginia, is attracting middle-class blacks and whites to the county.

In the aging communities near the District line, economic gains have occurred more slowly. To spur development, state, county and local officials have played activist roles.

In 1982, for example, the state created the Capitol Heights Enterprise Zone, a 70-acre triangle around a Metro rail station in which investors get an 80 percent abatement in county and town taxes for 10 years.

In Glenarden, developers were allowed to buy land for a new 47-acre industrial park and two new housing subdivisions from the city for a price lower than the market rate.

In October, the county will host its second annual investment tour in which developers and brokers will be shown potential development and rehabilitation sites in close-in suburban communities.

"We can't have decayed areas when we show developers the county," said Jeanette Ferguson, spokeswoman for the quasi-public Prince George's County Economic Development Corp.

Urban planners say that most of the county's older suburbs probably will never see the kind of splashy, large-scale development that has occurred outside the Beltway.

In addition, they say, developers are more likely to show interest in such cities as Cheverly and Glenarden, which are just off the Beltway and the Baltimore-Washington Parkway, than in less convenient neighborhoods. Such communities as Forest Heights and Oxon Hill, which are near major projects like PortAmerica, could see "a ripple effect across the Beltway," Langford said.

Building in these communities "is not quite as glamorous for a lot of developers," said Michael, vice president and general manager for Kenneth H. Michael Co., a land development, brokerage and property management company. "The projects are smaller, typically. There is a tremendous amount of time and effort that goes into the approval process for redevelopment. You've got to be able to work with local governments."

Kenneth H. Michael Co., developer of the 1.5 million-square-foot Ammendale business park in Laurel, is among firms making forays into the high-density inner Beltway area. The company recently completed renovation of a midnight-blue shopping center on Bladensburg Road in Colmar Manor. Within a month, the company plans to begin demolition of several other buildings north of the shopping center to make room for construction of a new commercial section. Investment is expected to total $15 million.

Farther east, in Cheverly, the company plans a $1.5 million renovation of Cheverly Terrace shopping center. Also in Cheverly, where homes now range from $90,000 to $120,000, the remaining acres of undeveloped land are being developed for two higher-priced subdivisions with homes that are expected to go for $170,000.

In Glenarden, where the county's first public housing project went up in 1969, Spriggs Construction Co. is building two new subdivisions with houses ranging from $135,000 to $170,000. Ten years ago, a developer complained to city officials that he could not sell houses in the same area for $75,000 and proposed to build a subdivision of lower-cost housing. City officials turned him down.

Walter L. Spriggs, vice president of the construction company, credited the county's improved image for the increase in Glenarden's new home prices, which two years ago had ranged to $100,000. He said the higher-priced homes sell to younger buyers who grew up in the community and now want larger houses.

"At one time Glenarden had a bad name," Spriggs said. "You had property that had just laid lax for a number of years and the area was becoming run-down. I think people are taking a second look at communities like Glenarden."

For Glenarden Mayor James C. Fletcher Jr., the community's outlook appears brighter for the first time in many years. "It's beginning to happen, but at a very slow pace," said Fletcher, who remembers a time 25 years ago when some homes in Glenarden had dirt floors, and chickens ran freely through city streets. "I see it happening."