Anonymous wrote:If they offer the job, before accepting, just ask them to clarify what they meant by a second way to pay you. They might just have a flat rate that covers your day hours but not overnight hours or something like that. Don't make assumptions that they were planning to buy dinner and call it even unless that's exactly what they said.
This.
If you get an offer you say "Thank you so much. You seem great and I'm very interested. I have a couple of questions, could you clarify the scope of travel that might be involved, and how you envision compensation for that being different that the regular rate? (and anything else you want clarified)
A job offer is the start of the negotiation. Use the agency if they do, or respond directly to them if that's how it happens. Good luck!