/diy/ - Do It Yourself

First time poster looking for some advice. I want to make a rowing bicycle.
I was inspired by this german engineers attempt www.rowcycle.de, but it's
not for sale yet and they say it will be priced in the mid 4-digits -
way outside of my budget. This american version rowbike.com looks way less
complicated but also not very interesting.
I plan to make it mostly out of recycled bits to save on cost. I've got
some understanding of mechanics but no real engineering experience.
I've got basic tools and can get used bicycles for next to nothing.
Looking for ideas and technical help to make a rowing bicycle.
Some of the things I expect to be difficult are:

1) Converting pulling motion into rotational motion.
2) Having the pulling handle return to starting point without creating too
much resistance that doesn't convert to rotational motion.
3) Decoupling wheel motion from pulling device when not actively pulling
4) Converting leaning to the side to turning/slanting of the front wheels

Where do you suggest I start? I was thinking of building a frame first that
cannot turn to the side, just to focus on conversion of rowing to rotation
and once that is sorted, begin working on turning.
So first a frame with 3 wheels, a sliding seat and a pulley connected to the
back wheel.
Anyone want to build one with me and share ideas?