I have an 3 year old Desktop with NVIDIA GTX 1070.
Do I have to upgrade to use lumens and nanites? Will it not work at all?
I was wanting to light my game maps with the powerful lighting features.
What GPU cards are industry minimums now for AAA level production?
Yes, you can, although there are some caveats.
I ran UE5 with a GTX1050Ti. Nanite does work, but you’ll need to put a ridiculous amount of complexity in the scene before you see it having any effect.
Lumen also works, but will eat about 1/2 your framerate.
If you are actually working in the industry, having an RTX2000 is a bare minimum, ideally 3000.
However, the most popular gaming card is still the 1600, so these other cards are really just for easy development.
Just to be clear, you can run UE5, no problem.
you also should not that if you are using Lumen, you will only be able to take advantage of software ray tracing features, NOT hardward ray tracing features: Lumen Technical Details in Unreal Engine | Unreal Engine 5.0 Documentation
Buying a RTX 3060 card today.
It is like having a PC in your PC, that card… 
Be aware some people are having problem with the 30 series and UE5, but this will soon be ironed out…