How can an overriding method return either const value or const reference?

I have classes like these:

class Base
{
    virtual const Room &getRoom() const = 0;
};

class Owner : public Base
{
    const Room &getRoom() const override
    {
        return myRoom;
    }

    Room myRoom;
};

class Renter : public Base
{
    const Room &getRoom() const override
    {
        return Room(); //this will not work
    }
};

void main()
{
    const auto& room = ownerOrRenter.getRoom();
}

This does not work because I am returning the reference of a local variable. But if I change the return type of Base::getRoom() to const Room, I will have to make a copy of Owner::myRoom every time getRoom() is called. What can I do?