The Home

The home is the base from which the establishment of all human infrastructure is able to grow from. It's the base of the skill tree so to speak.

Your home can move around and be fold-uppable, it can be a boat, a mud hut, a stone house, a long house, a brick house... probably even a green house. The point is that without a stable shelter the ability for humans to build technology, infrastructure and to a large extent social systems is severely reduced. There is a reason that employers or governments, especially from the industrial revolution onwards, tend to build street after street in close proximity to industrial centers.

But that's the ugly side.

The point is, without a stable, sustainable, as-permanent-as-possible model for a home we can't hope to have a floating village, nevermind city!

There are four or five foundational systems that need to be well and truly solved in order to create a completely sustainable network of homes:
 * Water Treatment
 * Waste Management
 * Energy Production
 * Food production

Interior decor and architecture are important considerations. Pretty low level ones (meaning they are close to the practical and tangible ). But you could have a lovely looking place that is cold, has no power and the toilet keeps exploding. That's not a good place to be.
 * Heating

One of these is already solved, technically: food production. Dumpster dive, yo! Though a food growing initiative could potentially be started. (See: entophagy)