Where should I rent an1 bhk? My options are: worli, parel, fort, colaba, Andheri, dadar, byculla and Marine lines. Budget is 50k.

rent one 1bhk in Antilla at Altmount road

50k per month will definitely get you a decent place in Andheri/ Dadar. No clue about other areas. When I say decent, I mean fairly liveable community with easy access to commuting options. If you are looking for social life/ night life, both these places have a few options, and are close to the Khar-Bandra area.

worli, andheri. Look at areas post mumbai central; marine lines charni road have horrible shady 1bhks in buildings which will fall any day.