I'm applying at various places for my second postdoc position right now, and it looks like a lot of positions are being offered by brand-new professors setting up their research groups. New young professors and postdocs applying for a second position seem to basically be the same age - which makes sense, because I myself intend to apply for faculty positions from my second postdoc.

I feel this is different from, say, a professor supervising an older PhD student. In that case, you still have an experienced professor mentoring a less experienced student. But in the 2nd postdoc/young prof situation, we're dealing with people who have had a very similar career arc to each other, with very similar experience to each other (give or take a couple of years).

Is this a weird situation, or is it pretty normal? Has anyone here been on either side of this sort of professional relationship? I imagine you'd basically end up as co-collaborators rather than a professor mentoring a postdoc?