November 3, 1986

To build a house, Kenneth Ranuga explained, you need sand and cement to make the bricks, and three-ply wood from crating for the ceiling and, most of all, time. Thirty-six years ago, he said, it took him most of a year, working weekends and molding his own bricks to build a four-room house for himself and Agnes, his bride of a few months, in this tumbledown black township. And since then, at intervals, he has embarked on modifications, building bedrooms as the family grew, removing inner walls to make a parlor crammed with armchairs and tables and cupboards. It is a largish room that bears the imprints of a householder's pride: the glass display cabinet filled with knickknacks and mementos, a television powered by a generator in the absence of an electrical hookup and family portraits hung along the wall.

Bus Passengers Dwindling Ridership on New York City buses has dropped 45 percent since the mid-1960's, a decline that is worrying Transit Authority officials.

When the dreaded ''migras,'' the immigration police, picked up Marcelino Castro a few years ago in suburban Conroe, he thought the game was finally over. So when the immigration police went after another Mexican, Mr. Castro escaped. Now he is preparing to emerge from the legal twilight zone in which he has lived since floating across the Rio Grande on an inner tube eight Octobers ago. Mr. Castro, born of Mexican peasants 28 years ago in the impoverished town of Zacatepec, is one of the uncounted millions of illegal aliens who believe they are eligible for amnesty because of the new immigration bill. 'My Dreams Coming True' Under the legislation, those who can prove they have lived in the United States since before Jan. 1, 1982, may claim permanent legal residency and ultimately American citizenship.

Economic growth slowed in October and could slow even more the rest of the year, the National Association of Purchasing Management said in releasing its latest survey today. In the report, one of the first indications of how the economy performed last month, 20 percent of the purchasers surveyed said that production increased in October, while 15 percent said that it fell. In the group's survey for September, 27 percent said production was up while only 13 percent reported a decline, the lowest percentage citing a drop since March.

When Saudi Arabia's oil minister of 24 years, Sheik Ahmed Zaki Yamani, was abruptly dismissed last week, worldwide attention was drawn to one of the world's more secretive royal families, the House of Saud. The family, estimated to contain 8,000 members, is led by King Fahd, 64 years old, a man known in the Arab world for being extremely clever, cunning and alert. Hence the sobriquet, ''the desert hawk,'' which his subjects sometimes apply to him. King Fahd became the ruler in 1982, with the agreement of senior family members, after his half-brother, the amiable, sports-loving King Khaled, died after a history of heart trouble.