The female models have generally said that they can make as much or more tokens as a single female on the camsites. So it is unlikely that any current reasonably successful female is going to want to cam as couple as they won't likely make as much and/or more as part of a couple show, and based on other posts on here some portion of the viewers in general seem to be bothered by the females 's they are watching having and/or admitting to a boyfriend/husband. Some portion of the viewers/tippers seem to want to believe the person they are viewing is all theirs, and do not what to think anyone else is involved with who they are tipping.
For the most part most of the cam couples appear to be real couples that are open enough to also be cam couples. So to be a cam couple you would need to have a SO that is open to camming as a couple. I have (under another username) cammed as a couple and it was a SO that I was camming with and I brought up the idea to cam, and she had not done any sex work before that but liked the feeling of others tipping and complimenting her to see her body. So you need to find a SO that has the right sorts of kinks, and is open to this sort of thing. For a current female model the indications are that you proving everything (room, lighting, internet, cams and cam work, and other work) and they get all tips would still not be a good business deal for them as they can make more camming as a single female with no indications of any SO existing.