I finally found a great web site of free Excel Spreadsheets for Entrepreneurs, about 150 of them. As a Mac user you’ll definitely be able to use them for MS Office on the Mac, but with Numbers there might be some issues with any conversion. Be aware that the more complicated the spreadsheets are the more chance there might be issues.
Here’s the link to Jax Software and the free Spreadsheets for Entrepreneurs. Since they are free, there is no support for them, but verify their usefulness for your situation.