Normally a two years lease is signed between both parties and in most cases there is no break clause in the first year.  However, most landlords will entertain a break clause in the 2nd year which is exercised by giving 2 months notice in writing.  In other words, the minimum duration is 14 months.

If you are from the UK, this may surprise you a little, with the minimum duration being 6 months more than the 8 month period over there. One should also note that deposits are held by landlords in HK as opposed to third parties in the UK.