true josh, but you would have to be really silly to say "oh, we are splitting the price of the plane legal or not". I would never engage in "random" chit chat during a ramp check. I also and well aware of what they can and cannot require you to answer without representation. If you even think that the the conversation is heading to "uncharted" territories, I would immediately shut up and contact a lawyer. Might be "jumping the gun" but better safe than sorry! AOPA has a "cheap" plane which would cover these occasions.

That said, I really don't think that there is a reg (well at least I can't think of the specific one) which prohibits spliting the costs of the plane for time building.

The issue is how the time in logged. Safety pilot is legit and legal, a CFII giving instrument is also legal, and a MEI giving dual should be no issue either.

As for the Regionals looking at the logs and saying "?" well that probably really depends on which regional and how bad they need people. As for Corporate, I would be willing to bet that a 100 or so hours wouldn't even raise an eyebrow. That is a legit way to get some time. it is common, and depending how seriously you take it; it can even be considered CRM training. I know i did some time building using a friends twin which I paid for gas only, and worked with another pilot to sharpen my CRM skills while flying to fun and exciting places.