How much driving do you expect to do in each car daily? I'm sharing a single charger between the Model 3 and Wife's Leaf, which is doable while I'm not doing much mileage. The Leaf needs charging every 2 days, Tesla once a week so it's fine. If my journeys went up then we would need a second charger.
I imagine that for people who are happy to charge at any time of day/night it could be quite easy to share but if needing to take advantage of cheap rate limited time slots that would be different.