So my main town is an actual cartidge, but my second town, which was a cycling town before amiibo cards came into play, is loaded on to my 3DS (I have the limited edition Animal Crossing 3DS that came with a copy of ACNL on it. Therefore I need an NFC adapter, I do not have one yet, but I do have a New 3DS that has the amiibo capability that is also Animal Crossing themed (Happy Home Designer) and that is what I use for the amiibo cards.
All that to say that I have to have the game on a cartridge to be able to put anyone in the game.
I don't plan on opening a shop though, these people on here are chomping at the bit and it would make Animal Crossing less fun for me, kind of like when I cycled through the town for peoples request. Anyway, I'll do them at my leisure if anything and contact people. But there are a select few people I will do it for indefinitely (the ones that talk to me a lot on here)