A NEW NEIGHBOR & WIFE MOVES IN, HE IS EITHER A INSURNACE MAN OR
LAWYER...HE BEFRIENDS HIS NEXT DOOR NEIGHBOR AND RUNS HIM OVER WITH
HIS CAR BY ACCIDENT BUT, INSISTS HE SUES HIM AND GETS HIM MILLIONS ON
A LAWSUIT.  THE MAN WHO LIVED HERE 1ST IS SOMEWHAT HESITANT ABOUT THE
LAWSUIT BUT ACCEPTS THE MONEY.  THE NEW NEIGHBOR FRAMES HIM FOR THE
MURDER OF HIS WIFE.  COME TO FIND OUT THE WIFE THAT MOVED IN WITH HIM
WAS ACTUALLY HIS MISTRESS AND HE HAD ALREADY KILLED HIS WIFE BEFORE HE
MOVED IN THE NEIGHBORHOOD.  THE FIANL SCENE IN THE MOVIE IS THE
ORIGINAL NEIGHBOR AN HIS WIFE ARE STANDING IN THEIR YEARD ON ACRES AND
THERE'S NOT ANOTHER HOUSE IN SIGHT....

I am certain that you are remembering "Consenting Adults," starring
Kevin Kline and Kevin Spacey. Spacey is almost unrecognizable in this
movie: he is blond and has a tan.

I recall the last scene vividly: Kevin Kline and his wife are moving
into a new house in an isolated area, with no neighbors.

Here are a couple of plot summaries:

"Eddie Otis (Spacey) and his pretty, soft-spoken wife, Kay, move in
next door to Richard Parker and his wife. At first, they seem like the
perfect neighbors, and the two couples quickly develop a close
friendship. Soon enough, though, we see that Eddie makes his money
being a scam artist. He pretends to get hurt by the Parker's car, and
then presents them with a check that will pay off all their debts.
Although they were reluctant to accept the money, they think that
Eddie is a good friend to have risked his life for them. This
friendship changes, however, when Eddie (always the risk taker), talks
Richard into a wife-swapping game. After this 'game,' all hell breaks
loose. There is murder, and all fingers are pointed at Richard."

Review Focus
http://www.reviewfocus.com/cat1037/prod117998/review1.html 

"Alan J. Pakula (All the President's Men) directs this urban thriller
about a composer of jingles, Richard Parker (Kevin Kline) and wife
(Mary Elizabeth Mastrantonio), who become uncomfortably close to their
new suburban neighbors, Eddy and Kay Otis (Kevin Spacey and Rebecca
Miller). Eddy brings an oddly carefree tone to their gatherings, and
soon introduces a few unorthodox ideas, including an insurance scam to
help the Parkers out of debt. The men begin toying with the idea of
swapping wives, but Richard dismisses it, until obsessive Eddy
persuades Richard to reluctantly sneak into Kay's bedroom. Richard's
fears are justified, when he discovers a woman gruesomely slain.
Framed and charged with the crime, Richard struggles to prove his
innocence."

American Movie Classics
http://www.amctv.com/show/detail?CID=55608-1-EST

I hope I have correctly identified your movie. If not, please request
clarification; I'll be glad to offer further assistance before you
rate my answer.

Best regards,
pinkfreud

***** absolutely correct!!!!  I have been trying to find this for 6 months...