Budget about S$3000/annum for bus, trains and taxis. that should cover for a family. But is is a start. Late weekend taxis from Changi are quite expensive. Rush hour from the East Coast area to Orchard area best part of S$20.
Just to recap what has already been said here; Reasonable housing, not near Orchard Rd, S$50,000-70,000 pa. International school for two middle school children, S$50,000 pa (for both), tax, S$18,000-25,000 pa. Those are the big ones. Food all depends on where you buy and eat. If you can buy at the 'wet markets' for your fruit and vegetable and Hawker Centres (street restaurants) you will save quite a lot. If you buy from the up-market super markets then you will pay.
Services are all pretty good almost every thing works and no obvious graft to deal with.
Just saw an ad' for an apartment on the East Coast area, three bedroom, breaking lease currently S$6000 pm.
Good luck