majlis perbandaran only take action if the general surrounding of the house is affected ...

for example -- you say cars (presumably belonging to the staff), are they parked haphazardly or obstructing traffic ?? ..... Trash -- are they properly disposed off ??

you can check whether the owner have proper permit to store the stuff at home ... some dangerous stuff (flammable/combustible/aerosol stuff for example) need special storage if stored in bulk
or else check with health authorities whether the products have permit