I have never seen wood trim that didn't require caulking. We're not talking about a GIANT BEAD OF CAULK, but caulk used to fill the gaps on wavy walls and joints that don't fit precisely. Whet's your plan? Fill the gaps with paint?.

IMO caulking just gives a nice clean look and not any harder to keep clean than anything else.

I would want the details on exactly which caulk he plans to use. A tube of cheap DAP, or anything similar, will dry out and pull away within a year. Especially if it's done right next to raw wood trim.

PPG's Top Gun 400 is the best I've found.

https://www.ppgpaints.com/products/adhesives-sealants/top-gun-400

There is a certain amount of time between when it's applied and when it can be painted.

When done correctly, everything it easier to keep clean.

Are you talking about caulking the baseboard where it contacts the wall, joints or the shoe contacts the baseboard or, are you asking about the gap between the baseboard and the hardwood flooring. The former should always be done, but I would not caulk the baseboard to the floor.

First...we did not plan to fill it with anything other than caulk. We have always done the painting ourselves in the past so first experience dealing with a professional.
So should the cost include caulking or is that a separate line item?
Of course I was referring to the wall, not the floor.
Thanks for some positive and constructive feedback.

I would always advise to have this caulking/prep process described within the painting quotation. You want to avoid a situation where the painter has assumed that this will be done by you and they only have to paint. Painting is painting and prep work is a separate additional task.

Caulking is part of a complete paint job. The task should be listed as part of the scope of work but would not be charged separately. You should have a complete price for the project and the painter should describe his plans and set the expectations for the results. Clarify with him who moves furniture, hangs pictures and puts up window treatments after the painting. Discuss your expectations for the amount of patching and prep work before the contract is signed. Discuss what will be removed and what will be painted around like thermostats, window hardware, switchplate covers, and wall sconces. If you have not used a professional painter before, dont be afraid to ask questions. There is not a single standard for what is included and what extra charges might be incurred, so just ask first.