Hi, I am getting into this mining thing I heard of on the www and can not decide on the GPU parts.

I could buy some used Radeon VII for 520$ each or should I wait for the new Nvidia or later AMD cards to be released?

Actually I am super hyped and want to start right away – already built up my first rig and mainboard. Or could I add the RTX 3080 or Big Navi later on to eventually existing Radeon VII? Will it cause any issues?