Ask the employer who approves a detailed duty statement and when each contributor can respond. Compensation teams, human resources and the hiring manager may have separate responsibilities. Set an evidence milestone based on their confirmed availability, rather than promising a standard number of days or weeks.
Ask both sources at once
Send the request to the hiring manager and to human resources in the same message, so the internal definition and the practical description are produced in parallel rather than in sequence. Give a deadline tied to the intended start date, and explain what the document is for. Hold travel plans until counsel has seen the finished description.
Work backward from the launch: evidence collection takes the longest, a port-of-entry application can be decided the same day, and an I-129 petition adds weeks. Not until the letter, the credential and the admission route have been confirmed. Do not assume unresolved material facts can be ignored because the employer wants an early start. For a port-of-entry application, plan to apply on a weekday with time to spare and not on the morning the lease begins, because a refusal or a request for more evidence needs room to be handled.