The bottom line here as others have said, is to have clear communication up front about what is/is not expected.
As a client, I would expect to pay for all meals, snacks, coffee, drinks, etc. Maybe some cash so they have some mad money for the week (this should be agreed in advance). I would also assume I would "splurge" for a few things, but those should be splurges and not expected. It should be a nice surprise when you do pick up the bill, and the provider should be grateful.
I could see some providers thinking they can go on a shopping spree, that's why it's important to establish boundaries up front so they know that's out of bounds.
It would also be important to discuss other things like:
- do he / you get downtime (apart) ?
- can you / he see other clients/providers or hookup while traveling together?
- is he open to hiring a 3rd if the opportunity presents?
- are substances permitted? how about drunkenness?
- what are your expectations about sex - frequency? limits? on-demand?
- is PDA permitted/expected?
- what's your body clock schedule? What time do you expect to start and end your day? Being a morning person and being with someone who is a late sleeper (or vice versa) can be annoying
- What are your habits - gym? Naps? snacks? computer time?
- What's your activity level? What kinds of activities or excursions will you do while traveling? Do you have physical limits or limitations?
- what are your food likes and dislikes (or allergies), traveling with a vegan could be quite limiting
As the client, I think it's primarily your responsibility to communicate your needs/limits and where you are willing to be flexible.