what's the boy scout motto "be prepared"
probably better imo to start a small company or just an informal group, invite a few people on board to R & D it & scope things, to establish its likely potential [assuming you haven't done this already] & let things evolve from there - if you want the patent protection then probably this nucleus or founding group should contribute both financially & intellectually, if the inventor doesn't have the means at his disposal which is more than likely.
This would be the route I would take. A small brain storming group with each picked for a specific skill, training and expertize. Mechanical improvements, working blue prints (CAD), simulation and animation software, patent drawings, patent wording, promotion, marketing, licensing, etc.
Being prepared is making sure your butt is covered, before presenting your patent, in the likelihood someone could change one small item and patent as a whole new machine.
Once your preparedness has paid off, then you can share with who ever and how ever you like!
Ralph