I think the best way to phrase your question would be to buy PBN links.
I don't think anybody in their right mind who put in the time, effort and energy to build up a PBN network properly would just hand over the keys to a random stranger.
I know that sounds harsh.
I know that it's probably not the answer you're looking for, but that's the absolute truth.
It defies logic why somebody would rent out their PBN on a wholesale basis.
As you probably already know, building up a PBN is no joke.
It takes a lot of work, a lot of planning, and yes, a lot of capital.
I don't think anybody would risk all of that just for a quick buck.
Now, with that said people will, can and do rent out links in their networks.
This is probably the way you should go about doing things.