Obtaining a temporary residency with an employment contract requires your employer has to be registered and him/she sponsoring your petition.
It is highly likely that the Immigrations Agency will conduct an inspection to verify that you are actually working at your employers location/office. If they don’t find you there after two or three visits, employer and employee can be summoned for fraud investigation. If confirmed that you are being hired as a “favor” just to obtain residency, the Immigrations Agency will likely issue a deportation order with prohibition to reenter the country.
If your residency is approved, you must remain on the payroll and make payments of approximately 30% of the declared salary in social security taxes.