As the sponsor, you must ensure that the applicant complies to the following during his/her stay in Singapore under your sponsorship:-
a)      Complies with the provisions of the Immigration Act and any regulations in Singapore during his/her stay in Singapore.
b)      His/her purpose of stay in Singapore is solely for social visit only.
c)      He/she shall not indulge in any activities which are inconsistent with the purpose of the visit pass (long-term or short-term) which was issued to him/her.
d)      He/she shall not engage in any form of employment paid or unpaid, or in any business profession or occupation, or in any activity which, the opinion of the Controller of Immigration is detrimental to the security, reputation and well-being of Singapore.

This information is sourced from ICA