Singapore is the land of rules and legislation. Please make sure you have the right pass to work, before getting commercially involved.
At the website of the Ministry of Manpower (MOM), you can find all information regarding the different types of work pass. MOM will usually assist you quite promptly by phone. You can send them an email to ask for advice, but expect a phone call in return. Do ask for a reference number of the call, which you can use in further communication with MOM.
After registration of your business with ACRA, you can apply for the type of work pass that suits your situation. It is advisable to wait 3-4 weeks after registration of your business before applying for a work pass; this way, all parts of the Singapore Government have had their monthly alignment. Since June 2015 it is no longer possible to apply for a work pass on your own behalf (via a paper form at the post office). A registered employment agency has to do this for you (via an online account called EPOL).
More information about Workpasses and Labour Law: