The serious downside is that the Ministry takes into account your "partner's" income and may disentitle you to social assistance benefits in that situation.
That's what happened to Mr. Street, who lived with another man in Vanderhoof. He was actually charged with fraud, because, according to the Crown, he had lied when he said that he was not living with anyone. The judge dismissed the charge, noting that he had responded to a question "Marital status - single, never married" appropriately since at the time same sex partners could not marry. The judge went on to find that though the two men were living together, the evidence did not establish a common law relationship, even if the two were "buddies with benefits" as the court put it, during that time. R. v. Street 2012 BCJ #2356 November 15, 2012