Boats?...mmm. The big problem is where to berth or where to drop the hook. Swing moorings are like RHS and live aboard marinas are very thin on the ground. Clear water bay marina have banned new live aboards and RHKYC Shelter Cove, the same. That leaves Db and debentures, HK Marina..(again, no live aboards), Gold coast or that swing mooring. Marina fees are around 6 to 15K, depending on boat length or beam. Cats occupy two berths generally, so double your figures there. I know of two larger catamarans swinging off anchors on shallow water but dinghy access for them is at times , a problem, particularly when the 3 or 8 signal is up.
It may be worth looking further North tho, if you want to live ashore..Fan Ling, Shen Shui and then pick up a reliable car for the 1hr commute.