hiring domestic helper with under 15,000hkd monthly household income

We would like to hire a domestic helper. I am fully aware that the minimum monthly household income must not under 15,000 hkd. Would it be possible to hire someone if I will provide my monthy income together the monthly income of my friend who also lives with us?
One more thing is, the helper we would like to hire will expire her visa 3 days from now, does she needs to extend jer visa while we are on processing or what should we do so she wont over stay her visa. We dont plan to use any agency services as this helper is finished contract and can process her visa on her on accord.
Any help or advice is much appreciated.