。
Is it convenient for you to start work tomorrow?
Literal
Tomorrow [from-から] work [object-を] start [nominalizer-の] [topic-は] you [toward-にとって] convenience [subject-が] good [polite-です] [question-か].
~にとって marks 'from the perspective of X' / 'for X' — essential for expressing subjective relevance. 都合がいい is the set phrase for 'convenient' (literally 'circumstance is good'). The subject of 都合 is implicit (your circumstance), and the overall sentence asks about suitability to the listener. A polite work/schedule check.