I'm imagining a world where it's possible to travel back in time, but doing so creates an alternate universe rather then changing your past. There is some high, but manageable, cost the first time you go back in time and create a new universe, then it's relatively inexpensive to move between the two universes after they have split. New worlds can only be created by traveling back in time. While people from a 'past' timelines can travel to a the universe they originally diverged from they can't travel to their new universes future.
I'm imagining a sort of post scarcity economy being developed that uses time travel to provide us with required resources. The basic idea is that you open a portal to a 'past' time line that has abundant resources and is willing to pay large quantities of those resources to you in order to get your advanced technology. Each side wins in this trade. Eventually the 'past' universe may run low on raw resources, but by then they would have built up their own tech base and have the ability to use the same trick of using past timelines to provide them with more raw resources.
To combat over population new universes can be created so far back in time that there are few, if any, homo sapiens on the world and constantly be built up as new colonies to spread into as the current world becomes over populated. I imagine at some point a particular world may still have issues with things like global warming and might need abandoned for entirely for a colony universe, but if they can be set up fast enough this is an inconvenience but still allows a high quality of life to people even if they occasionally have to move to a more convenient universe.
My question is rather this works from an economic perspective. Can resource scarcity be solved by the constant creation of new universes in such a way that a modern human has a much higher quality of life? I also want this system to be non-exploitive, the people in the 'past' timelines should be benefiting from trade and not be terrible exploited by the future timelines; which I think is possible so long as you help build up their technological base to the point they can start creating new universes to feed their resource needs before their own resources are fully depleted. Basically it's a pyramid scheme that actually works because you never run out of new universes to continue to perpetuate the scheme.
Is this economically viable? If not where would the economy or system fall apart?