The judge also ordered James Duncan Keats to provide a DNA sample as he will be added to the National Sex Offender Registry for 20 years.
Keats was convicted in June of assaulting the woman in the upstairs bedroom of her home in 2013 while his partner tended to her ailing husband downstairs.
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Keats was found not guilty of a second charge of sexual assault involving the same woman in 2012.
He was also acquitted of two counts of breach of trust.
The Crown had said previously it would seek a prison sentence of between five and seven years.