work permit dependant visa query

Hi all,
Im on IT work permit for 3.5 years now. Im applying for my wife to come join me here. I have got all paper work i fink, 3 months payslips, employment letter, 3 month bank statements.
The only confusion is about accomodation
Im living with my grand parents rent free, no bill is in my name ,except for my mobile phone bill which has the address im living in. The house got 3 rooms ,grand parents living in one . Will it be enough to write a simple letter stating im livin with them rent free and get it signed by my grand dad. Will that be enough. Thanks