Typically the credential costs: licence applications, examinations, credential verification, and translations of French-language records. The government fee for the route chosen appears in the USCIS fee schedule and is often paid by the employer for a petition, while a border application charge is usually paid by the applicant.
Ask which side of the ledger each item lands on
Three groups of costs exist, and who pays each is a negotiation, not a rule. Government charges are set in the USCIS fee schedule for an I-129 petition, with an optional premium-processing fee, and at the port of entry for an application made there; many U.S. employers pay the petition fee as a matter of policy and rarely pay a border fee they are not present for.
Credential costs are almost always the applicant's: a state licence application, an examination, a primary-source verification of a Québec diploma, and certified translations of transcripts. Hypothetical example: a Sainte-Brigitte-de-Laval nutritionist is told the employer will cover everything, then finds that everything means the petition fee and that her licence, translations and exam total more than the fee itself. Ask for the cost split in writing with the offer, check the current G-1055 figures rather than a recruiter's summary, and keep relocation and family expenses on a separate page since they are irrelevant to eligibility.