QB Issue Resolution:

You have to pay for two. With QB online, each company costs more.  Even with only one company, QB Online costs far more than QB desktop.

Resolution for Issue 'I have QB 2013 for MAC. I run a small business and a rental property separately. Can these upload into one online account or do I need to pay for 2?' available: Yes (Solved).
Source: Intuit Community forum.

I have QB 2013 for MAC. I run a small business and a rental property separately. Can these upload into one online account or do I need to pay for 2?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for company costs
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Error Recovery for company costs [Canada]
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