Using Quickbooks 2013 Pro

You can use the same QB software for multiple company files. Beware--QB is known to be prone to data corruption if your data files become too large and/or complex. QB also has some accuracy issues. You might want to consider software that is actually a little more friendly to running multiple entities, whether related or not.

I'm a member of the Sage Accountants Network and I use Sage 50 Quantum 2014 (which is a rather expensive version). I own several un-related environmental, solvent and service companies that actually do business with one another. Sage 50 Complete (and higher) versions will not only allow you to keep multiple company files open at the same time, they will allow you to consolidate your financials into a 'shell' company file as well. This would allow you to view unrelated companies as a portfolio, while maintaining them as individual companies. You can consolidate up to 20 companies, which is plenty for the small business owner.

Quickbooks is less expensive for a reason. I've learned my lesson about relying on their overseas-based tech support. Sage 50 is US-based and it makes a BIG difference when there's tech support needed.

I urge you to return your copy of QB and take a look at Sage 50 instead.