Work contracts are rarely longer than 2 years – often only for 1 year. The company that hires you is obliged to handle all the legal procedures and to arrange the KITAS for you. For that, you need to submit a set of documents such as your CV, passport etc. Your CV must reflect your qualifications for the job. Usually, the KITAS takes several months to be issued and is applied for you while you are still abroad (offshore KITAS). Most HR departments work with a visa agent to get the job done. THE KITAS is usually valid for 12 months (some only 6 months) and then needs to be renewed.
The company is also obliged to pay a monthly tax of 100USD for you – in advance. This is called DKP-TKA (Compensation Fund to Employ Foreign Workers). With the KITAS you don’t need a different visa in order to freely travel in and out of the country as it is multi-entry. The company will register you with the domestic social security system and fees will be deducted from you salary. And you will receive a local tax number and pay income tax, which will usually be automatically deducted from your salary. It’s always the easiest – at least for the employee to negotiate a take-home pay, like this you won’t “care” how much the company will have to additionally pay on your behalf.