As far as I understand, there are two things required for qubits in quantum computing

1) They're entangled
2) A single qubit does not simply have on/off state, but instead its state is represented by two complex numbers

Point 1 is pretty crucial to quantum computing as far as I understand.

But point 2: this means that the state of a single qubit cannot be represented by an integer, but requires two complex numbers (and k entangled qubits require 2^k complex numbers)?

The question is: what precision is needed for the complex numbers (their real components), if you were to simulate qubits on a conventional computer?

Thanks.

You don't need super high precision to simulate a quantum computer. Existing simulation libraries use both single and double precision IEEE floats.