abraham1723, do not mislead the guy.
Australians can obtain a visit visas upon arrival at the airport for 1 months (QR100).
Any of your friends/visitors can stay at your apartment with no any problem whatsoever. By the way, your profile says you are under 18 (??) Are you with your parents here?
Married couple would need a marriage certificate only if they are planning to check in to some hotel. Other than that they should be fine...

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“You become responsible forever for what you have tamed”. Antoine de Saint-Exupéry