It turns out that the marmoset is the world's smallest monkey. I can vouch for its tiny size. The one I saw looked a lot like the one in the picture. It had the tiniest hands. It also was very active, jumping from tree branch to tree branch in its cage. They are active during the day and they live in trees, so the habitat the zoo provided was a match for the little primate.
When I walked up next to the cage, it jumped closer to me and looked at me with its bright and curious eyes. It made some small twittering sounds as it fidgeted with the tree branch.
Another group of people walked up to the marmoset's cage and the children asked their parents if they could have a marmoset. One of the parents remarked that having one might be really cool. Uh, I think marmosets are adorbs, too, but... having one as a pet? No thank you.
Because these guys are tree dwellers, they would need that type of habitat at your home. If you decided to let it run free in your home -- bad idea -- it would likely climb up as high as it could and knock things down at will. Also, do you really think a marmoset is potty-trained? Sadly, no. Monkey dung would end up all over your lovely home in no time.
Another thing these little cuties do is mark and defend their territory. I don't know if humans can smell the scent-marking or not, but it doesn't sound like a good thing for your furniture and other personal items.
Even though I wouldn't want to share my home with a marmoset, I think they are really cool animals in an environment suited to them.