A contract is a very important document. The contract must be one that has been registered at the Labor Office without which it has little value. If you have a legal contract from your employer, you can seek the assistance of the Labor Office should the employer make a breach of agreement. Without a legalized contract you are left at the whims of the employer. He may not pay you your salary for example or not give you your End of Service benefits as required by the labor law, and you will not be able to make any claims. If he is willing to give you a contract after your arrival here, it is fine as that is how it is done in most cases.