virtualbox.org

I need Windows on my MacBook Air in order to run one piece of software.

I don't want to spend a fortune so I have some questions.

Would VirtualBox allow me to switch from Mac to Windows and back to Mac easily?

Would VirtualBox allow me to run this software (AntiqueSoft) on my Mac?

Thank you for your help.

Pass on the application question. VirtualBox is a PC simulator: the whole of the simulation runs as one application on your Mac host - so yes you can easily access host and guest at the same time, especially if you install the guest additions to improve integration.

Perhaps you don't even need a VM. Have you checked if the application runs under Wine/WineBottler?