JIMMY GOH

Hi, I have a garden behind my semi-d measuring 16.409mX9m(SPLAYED AREA10.5M at eastern flank) which I like to convert to a 4 storey annexe bullding, level 1 be connected with the exsiting building as part of an open concept kitchen + an elder friendly room with the top levels having 5 rooms + top open area(balcony), all rooms with attached baths, aircon etc. Budget is $500,000. Access to the garden by the side has a 3m width. Can this done and approved by all the relevant authorities.