The official material describes the process in terms of weeks, but that is a description rather than a guarantee, and no exact date can be promised. Plan for an open-ended wait between paying the fee and receiving USCIS instructions. Avoid resignations, property sales, or school enrolments that depend on a particular response date.
Decide what happens if nothing arrives
Agree in advance how long the household will wait before asking counsel to check the status, and through which official channel that enquiry is made. Set a review date in the calendar rather than checking email anxiously each morning. Keep documents current in the meantime, since passports and civil records can expire during a wait.
Nothing should be paid to a third party promising to accelerate an official step. Agree in advance how long the household will wait before asking counsel to make an enquiry, through which official channel, and who makes it. Put the review date in the calendar so the wait does not turn into a daily check of email.
Descriptions of processing in weeks are descriptions rather than commitments, and no exact date can be promised. Avoid resignations, property sales, lease terminations, and school enrolments that depend on a particular response date, since each one converts a delay into a loss. Keep documents current during the wait.
Nothing should be paid to any third party offering to accelerate an official step, and any such offer is itself a reason for caution.