NEWPORT, R.I. (AP) _ Newport is a town of millionaires' mansions and America's Cup yachting but a hard place to live on a sailor's salary, according to enlisted personnel and their families.

Few apartment rentals are available for under $500 a month, and there is a waiting list of up to a year for government housing. Real estate agents and U.S. Navy officials on Aquidneck Island, where Newport lies, say there is no easy answer for sailors' housing woes.

''My heart goes out to the enlisted people,'' said William K. Mallinson, a retired Navy captain and president of Island Homes Ltd. ''In many cases, they have got to take something substandard or get off the island and go to Fall River (Mass.).''

The Navy once stationed 41 ships at the Naval Education and Training Center in Newport, and the town had plenty of affordable housing. But most of those ships were transferred to Norfolk, Va., in 1973, and personnel at the base dropped from about 18,000 that year to 4,300 two years later, said Navy spokeswoman Janice Anderson.

Most of the apartments once inhabited by Navy people have been abandoned or converted to condominiums or single-family homes, city officials and real estate agents say.

''This is the premier condominium area in the state,'' said Stephen Ostiguy, director of Church Community Housing Corp., a Newport-based, non- profit association.

The booming tourist trade and several new, defense-oriented technical companies have caused rents and property values to rise steadily, noted Mallinson.

About 3,700 people are permanently stationed in Newport, but there are only 1,450 housing units at the base, Mrs. Anderson said. Two thousand Navy students on short-term assignment to Newport live in dormitory-style accommodations, she said.

Plans to fix up 186 units have been stalled because the U.S. Senate has not released $22 million authorized for Navy housing construction, Mrs. Anderson said.

For Navy personnel from less-affluent areas, being assigned to Newport can be an eye-opener.

''I've never seen so many BMWs and Jaguars in my life,'' said Lt. j.g. Curt Curavo, 27, an assistant plans and operations officer. ''I was coming from an apartment in northern Michigan. My wife and I were paying, for a two-bedroom, $225 a month.''

Chief Petty Officer Ron Ammons, who was transferred from Charleston, S.C., in October 1985, said there was no comparison between the cities.

''In Charleston, I could buy two houses for the price of one here,'' he said.

But Ammons, a career counselor at the base who lived in a $525-per-month apartment while waiting for a vacancy in government housing, said most military people can afford to live in the area.

''Most people stationed here are at least E-3 (seaman),'' Ammons said. ''An E-4 (petty officer third class), just on what the Navy gives him for housing allowance, he could handle $550 a month rent.''

A petty officer third class with four years' service in the Navy makes $981 in base pay a month and is eligible for up to $422 per month in housing allowances if he has dependents, Mrs. Anderson said.

But the wife of a petty officer third class who is stationed on a ship at Newport says they have a tough time, even with his E-4 ranking.

''My heat bill is $200 a month,'' said the woman, who spoke on condition of anonymity. ''And with the rent ($475), that eats up most of our paycheck,''