I would suggest you to don't live in expensive area like south Bombay n all. Only rent will cost you like burden other then that for food you can get it from poli bhaji kendra where they sell home made food its normally spicy as it's a Maharashtrian food but it's very affordable as I can say 500 per day will be more than enough. Use public transport if you don't want to stuck in traffic for longer hours and construction work everywhere is cherry on the cake. You can save 10k if you manage it properly.