When costs are high and so are your business telephone needs, sometimes choosing a second hand system is exactly what you need to do. But this usually results in additional problems. How do you know the system is still performing at its best? This is how you need to evaluate your pre-owned equipment.
Companies that offer pre-owned equipment should refurbish, review, clean-up and intimately assess the state of the system before selling it. To find out if they do this, speak to the sales people and ask them about their evaluation process.
You can always invite a business telephone systems engineer to check out a second-hand system that you are interested in. They know more about it than you do, and will be able to see immediately if anything is out of place or broken.
Always look for a guarantee on the business telephone system. Guarantees are great because if something does break, the company is liable and they have to replace the broken part. There are usually twelve-month manufacturer warranties as well.
Short of getting an expert to help you, you can also test the system out for yourself by installing it and seeing if everything works efficiently. Tell your employees to make a note of what does not work. Then hand this list to the service provider.
If that fails, try educating yourself on a more advanced level about business telephone systems. This book does a lot to educate you, but you can also use Internet resources to check-up on certain performance features as you go.