Dependant applications, any travel they require, childcare, and the cost of the spouse's job search, including credential assessment or licensing steps in a regulated field. There may also be legal time spent confirming how the spouse's status evidence should be presented to a prospective employer.
Budget for a search that takes time
The realistic risk is not a fee but a gap: several months on one income while the spouse searches. Decide in advance how long the household can absorb that, and what it would do if the search runs longer. Ask counsel to quote the dependant work separately from the principal's case so the household can see what the second half of the plan actually costs.
Hypothetical example: a spouse working in medical device sales assumes a search of six to eight weeks and takes five months, partly because a state registration was required for part of the territory. A first review would have identified the registration at the outset and asked what it involves, then budgeted for both the search and the licensing step. Ask counsel to quote the dependent work separately from the principal's case, and ask specifically whether advice on presenting status evidence to a prospective employer is inside that scope or billed as it arises.