A few legal points, which are needed.
Employee compensation insurance - for an office environment it is quite cheap, and it is dependent on the number of employees you have
MPF - already mentioned above
Taxes - although you don't need to make payroll deductions you do need to inform the IRD that you have employed someone and you need to send the employee a IR56B at the end of the tax year and a similar form to the IRD.
Visa - if you are not a PR/Dependent Visa holder you need to get approval from the IMMD for yourself for an investment visa, or if you are doing this outside of work, you need your employment visa modified.