Ask about the language the software is written in. Some languages are at the end of their life cycles and close to becoming obsolete - which results in software without a future. Make sure the language used creates true Windows applications, is mainstream, and is widely used, such as PowerBuilder. Ask about the database. The database should also be able to handle the volume of transactions your business generates.
Many database are great for low volumes, but choke when the transaction rate increases.
The more orders a day you process, the higher your transaction count. And, since you expect your business to grow, you'll want a software program that can easily grow with you. The only thing worse than dealing with software that needs a specially trained computer operator to run it is having to use software that runs slowly. Remember, every software package runs fast with the test data provided by the software developer. Make sure the software can handle YOUR volume of business, and that your employees will be able to learn to use it quickly and easily without having to get certified in the program or keep their noses stuck in operating manuals.