Help with mold and caulking for bathroom

My family's bathroom (bathtub shower) needs to be recaulked, the mold is bad and they've been recaulking incorrectly for years (possible water damage?). There is definitely mold behind the caulk.

Does anyone have any advice on what to do about it?

I wanted to pay a contractor to recaulk and do a minimum or temporary mold treatment, is there anything to look out for so I don't get scammed?

What experience did you have trying to recaulk or fix mold?

Is it expensive?