I would say you need to develope a relationship before diving into anything. you can take a look at their operation from a pilot standpoint, but the best thing you can do is ask to see some of their trip manifests, ops specs, see that things are in order, talk to their director of maintenance etc.... In most situations, the 135 will have more to gain than the owner, but with that said there are mutual situations that im sure work out there.

Im trying to get on a new 135 cert of a guy i used to work with years ago. He's in this situation where he's looking for another aircraft to help cover, and reduce the risk of not having a plane available. He's had plenty of "promises" but no one has come through, so it apparently is the same on both sides of the fence.