How can they be level 0 and also be a class???
Have done in the past, sure. 3e had rules for 0 (or even negative) levels, they were kinda meant for MCing, but could be used the way you described. "0 level" was a thing for NPCs in the classic game, at times I or a DM I was playing under would include the 1d6 hps 0-level NPCs got as just a way of giving first level characters more hps, or even have them play '0 level' for a little bit to get them.Anyone try something like this? Caveats?
However, 5e's level 1 is enough like a 'level 0,' that I don't feel a strong need to try anything like that. You could run backstory where the players pick Race, play through bits of their early-life backstory, choose Background, play through a sort of coming-of-age backstory, then choose class and get started with more traditional play, if you wanted to - probably want to avoid much actual combat or anything in that process, though.
That'd be an example of 'avoid much actual combat,' yeah, assuming the players were sufficiently clueful.Or run it with combat situations that the players must desperately try to avoid.
However, 5e's level 1 is enough like a 'level 0,' that I don't feel a strong need to try anything like that. You could run backstory where the players pick Race, play through bits of their early-life backstory, choose Background, play through a sort of coming-of-age backstory, then choose class and get started with more traditional play, if you wanted to - probably want to avoid much actual combat or anything in that process, though.