Franz, I understand these hesitations - but Greg has got the point. Check again, (and ask users or factory), what is included, and what else you might need. Comparing Fujita 500 double with K1 single isn't fair - if you want a narrow double, Klondike would've been closer. But it costs more than K1. And (don't remember for sure) I think Klondike has more payload, than Fj500 (which is still not too much, - Klondike is a medium-short touring double). And Klondike can be paddled from midship position, but Fj500, as I understnad - can't. For a first try you might as well buy one of Folbots, - GII, fore example, - it is probably cheaper than Fj500 (check their website - they have sales all the time, - trying to lure new customers

), and try how it feels paddling from the rear seat. It is wider than Klondike or Fj500 - so it is not the same in handling, but you'll know how close or far this is to your goals.
PS: I have no connections with Folbot or Fujita - own one Feather and one LH currently. Whicheverver of them you choose, it will be fun, I'm sure.