Question, what happens exactly in multiplayer mode? Can you fight enemies live with other players, or do they simply hang around the towns? I'm hoping I can play with my husband but I wanna know it's worth the extra money.
One thing you need to know about multiplayer is that if you don't have the DLC, then you can only play with someone who doesn't have the DLC either. And if you do have the DLC, then you can only play with people who have it as well. So say you get the DLC, but your husband doesn't, then you won't be able to play together.
Traveling to another world is done in only a few seconds. It is much faster than ACNL where you first have to talk to Porter, wait for the train to arrive, get on the train and so on. It's one thing I absolutely love in FL.
In multiplayer you can trade items using the red box in the guild office (either items you find/buy or that you craft). Make sure to pick up the items before ending the session or they will disappear! Though the game warns you about it when using the red box, so I don't think you'll have any problems there.
You can indeed fight enemies together! Best thing is that it counts for your challenges as well! The only thing you might want to decide in advance is who gets the bounty. Be careful with bounty boxes, though. Other than the fact that they can be destroyed, only three can exist in the world at the same time (so if you get a fourth, the first one will disappear) and I am not sure how exactly that works in multiplayer (say you have three bounty boxes and your husband gets one; will one of yours disappear or will there be four boxes?).
There's also an option to teleport to where the other is. So let's say you are in X because you want to defeat Y; your husband can teleport to where your character is, rather than having to run there all the way. I can't exactly remember how it's done, but I believe that there's something like "Go to" and it'll show your location (been a while since I last played the game).
I think you'll especially want to play together if you do decide to get the DLC. The Tower Trials can be quite challenging but they're a lot of fun too! You can beat those on your own, though, with or without NPC's (though, obviously, without NPC's they can be quite hard!).
The DLC expansion is already included in the game, by the way. You download a "key" from the eShop; from what I remember it takes two blocks or so on your SD card.
Oh, and important as well; you cannot travel to a place on the map that you haven't unlocked yet. So your husband wouldn't be able to travel to the second town in your world if he hasn't beaten that chapter of the story yet.
And I think that's everything. Sorry it's so long, but I hope it answers your question and helps you. ^_^