In Option (1), "going into business" correctly refers to entering or starting a business venture.
In Option (2), "runs a profitable business" is correct as it indicates ongoing business operations.
In Option (3), "get twice as much business" refers to the volume or scale of business, which is appropriately used here.
In Option (4), "as much my business as yours" is correct in the context of something being of personal concern or interest to someone.
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