“Many successful public history careers are built on the ability to collaborate or partner with various individuals/groups/stakeholders. What scale of potential earnings is necessary to motivate SERIOUS participation in unconventional collaboration?”
I think that this question is very subjective and situational. I am uncertain how our individual answers would produce helpful dialogue regarding new careers, but I will take a stab at it anyway and look forward to understanding later. I think that if I had a stable income with an acceptable employer (which I do now) that I would be highly unlikely to risk the loss of that income by undertaking a project that could possibly cause that loss – unless there were many open positions at a similar level in my desired geographic area to replace it. If I did not have anything to lose or was unhappy with my work environment, then I would be more open to taking on the risk of such a project. If I had a solid safety net, or was independently wealthy, then I would also be more apt to participate in an “unconventional” collaborative project. As an example, I have a stable income but am motivated to work towards a career change so I am undertaking the rather unrisky option of earning an MA one class at a time while keeping my full time job. This requires swapping some time that could be spent otherwise for studying time over several years.