Per diem

Latin for by the day. On a paid trip the client covers travel and accommodation directly, then hands over a set amount for each day so you are not chasing receipts for coffee and taxis. Rates vary with the city and with who is paying. Pin the details down in writing before you go: the daily amount, whether travel days pay full or half, whether meals already provided on set get deducted, and when the money actually arrives. Check the tax position in your country too, because a per diem above the accepted rate can be treated as income.