I subbed NIN to THF and had a pretty easy time getting parties (I think its the mentality of "he has NIN! he must be special!"). I would not recomment startign as THF though, its a really rough job before 15, and even after that its not overly easy to get parties compared to say NIN, PLD, WHM, BLM or BRD.

Hope that helps you out a little bit. Oh and think of an online game kinda like the forum.. lots of people on and off of it all the time, but you make parties and kill stuff in game with them. Its like a chatroom with and RPG engine attached to it so you can talk about and play a game at the same time