At the time we meet a person, we have caught him mid-story -perhaps on page 322, paragraph 5. He has read all that came before because it is his life, but you have not. You are only looking at that page, and mentally writing your own thoughts entirely for pages 1-321. You’ve even supplied your own prologue, prequels, and alternate series set in the same world.
I recommend this approach for someone who will likely take advantage of you. You may be three hundred pages in; but know, from other stories of scowling street stalkers, that caution would be wise.
That aside, let’s remember that a new person is a new chance for both in the encounter. He and we are perusing people, and the future has not been written yet.