I am on the verge of accepting a job for a consulting firm. The job has 30% travel. What pitfalls and cons are there?

For example, after working with the client during the day, would I be exploring solutions for them at night?

If I did that, do I get paid for all the hours I work, or only for "contact hours" with the customer?

What if I am in the office between customers? Am I paid for that usually?

I know I can ask this in my next interview but also want to do my research.

Thanks!