Agencies vary in what they cover. Ask in writing whether legal review, document preparation, credential evaluation, and travel are the agency's responsibility, the client's, or the professional's, and what happens to those costs if the assignment ends early.
Put cost responsibility in the contract, not in an email
Where three parties are involved, an assumption that someone else is paying tends to survive until an invoice arrives. Get the allocation written into the agency agreement, including reimbursement conditions and any clawback if the professional leaves. If the professional's own corporation forms part of the arrangement, note that advice about that structure is a separate cost from preparing the case itself.
Get the travel, mileage and lodging terms in writing alongside the duty description, since a broad territory can mean substantial unreimbursed cost. Licensing costs are set by the regulator and are unrelated to immigration fees, so treat them as two separate lines. The petition adds the Form I-129 filing fee, any asylum-program fee and optional premium processing, all listed on Form G-1055, plus the professional time to prepare the exhibits. Do not fold a spouse's or child's TD costs into the principal's line; they are separate people with separate charges.