Depends if you stipulated a contract or not.
If not, then id make sure you do the best job you can on it for the 1st pass. Beocuse if they aint happy with the clean they will go somewhere else at the drop of a hat.
This is why one 1st cleans for commercial the price was a good 65% more for the first clean; with the rest being the regular price for the service cleans.
If they are under contract with you for x amount of cleans; then you have less to worry about on your 1st clean as they are committed to you. I used to take a 50% upfront fee with the balance due on completion on each clean thereafter.
Commercial is tough and there is no loyalty; it can be lucrative but only until they dump you for someone cheaper.