According to Shia, Who is Wajib-al-Haj?

As far as I know, going to Haj is not mandatory for those people who cannot afford to pay the expense of this trip. But my question is that how we can recognize if it is Mandatory for us to go to Haj (or actually we are Wajib al Haj)? (Shia viewpoint) In fact, is there any specific factor(s) which show it? For instance, Will it be mandatory (Wajib) for us if we can provide its ticket expense by selling our gold or car and so on?