It's late 2017, and aliens finally arrive on earth.
They're very happy to meet us because we're the first civilization their generation ship encounters, and they freely share the two technological devices that allowed them to travel for thousands of years: the "Zero-Point Engine" and the "Energy-Matter Converter".
The instructions to build them are given to every single state, and they can even replicate themselves, so they quickly become widespread in the whole world (but are still government-regulated, a private citzen can't own one).
The "Zero-Point Engine" generates a constant amount of electricity from nothing.
The "Energy-Matter Converter" is an electric device that (almost) instantly materializes any blueprint, no matter how complex (think limitless 3D printer). It has no problems producing food or organic matter, in fact you don't need to create blueprints from scratch, as it is equipped with a scanner and will be able to produce exact copies of what you scan. It also has drones to make big things like buildings, cars and such.
Humans obviously need regulations on what they can/can't build, so I need some sort of "Replication Credits", to regulate the usage of EM Converters.
However, most people are left unemployed: all of manufacturing, ore extraction, agriculture (and more) is now useless.
There still are careers that resist and are even required: administration, research and developement (any field), hospitals, programmers...
So I am in a society that still has the need to work, but the majority of people are unemployed and they're not even expected to find a job.
How can I distribute credits in a fair way?
Things I already thought:
Daily amount of credits:
This would be unfair to those that work. Why should I work if my neighbor that does nothing gets the same? If we introduce paid work instead, we get inequality in the other direction: How should I get a job to gain more credits, if there are no jobs for the great majority of the population?
And let's get real: most humans must be forced to work for profit. Voluntary work exists, but is usually not long-lasting and not what society really needs in that moment (I still have to see voluntary data entry clerks or voluntary cleaners).
This would allow me to retain paid jobs, but would introduce a huge amount of problems, as there would be an immense hit to productivity and quality.
The end result
The great problem humans would face is lack of space and regulamentations on how to use your own ground. My story will see humanity trying to overcome that by building giant space "shells" around earth, and will revolve around the colonization (and building) of those first giant ecodomes. It's particulary important for me to figure out what exactly people on earth are doing to earn their abitable space and build things, as this will heavily influence how and why people get the right to colonize this new environment.