I consider myself a knight, yet the only armour I have is my fencing kevlars. ^_^
The problem with a discussion like this is that the definition needs to be flexible. If you put down that knight needs these qualifications, people who deserve it may not classify, and those who do not deserve it may. When a set system like that is put into effect, over time the system becomes bureaucratic and heartless, which is not something we, as knights should stand for.
The way my Order selects knights, and the way we recommend to the movement we started, is that a candidate is a knight if considered knightly by all existing knights of any given order. If they can impress all in an order, then they fit the qualifications FOR that order, and if they should be approved for an order, they could be considered a knight. Whether or not they choose to join said order, or remain a lone knight is up to them, but from the point that they are approved for an order, they classify as a knight.
As for knightly living, it's merely a title. If you consider yourself to be living a knightly existence, then you can classify yourself as a knight. But a self-given title is worthless if you are the only one who acknowledges it. You have to live knightly, and have people think you are worthy of such a title before it is of any real value.