Pig owner here. Keeping a pig in an apartment is going to be a little rough. You'd have to get them used to letting you put a harness on and walk them like a dog. I own my home, so I put in a huge dog door, worked great.

Probably the biggest problem is their intelligence and destructiveness. You'd have a huge job keeping a pig from getting bored when you're gone. Maybe they can be crate trained? Mine figured out 3 different ways to get into the beer, even defeating a baby lock, and got hammered. He does love him some beer.

Hooves were a huge pain when my pig lived inside. They never got a chance to wear normally and I played hell getting him back and forth to the only vet in the area that would trim him. Even the local farrier had never done a pig. All that hassle, and I live on the edge of town in a redneck suburb. I seriously doubt you're going to find a large animal vet in the city. You could probably work out the hoof thing with a rasp and 3 or 4 beers (for the pig, but you'll both need that to get through the ordeal).

If it's a male, you'll probably want to trim his tusks once or twice a year. I got that done on the nail salon trips.

So, you'd have to get the pig used to a harness and car rides, find a vet or farrier for his hooves, and crate train him.

Oh, one other small thing. Once or twice a year, depending on the animal, pigs "blow coat". This is not anything like shedding. ALL OF THEIR HAIR FALLS OUT AT ONCE. So there's that to consider. :)