Webmin is free and a start.

VPS control panels are generally really low costing - 4 to 10$ a month depending on provider. However as the story goes - what you want back from a control panel is how much you will invest into it.

A CPanel for VPS would cost around 5-10$ a month...

For dedicated servers you look at around 20-25$ (OR LESS) per month for the same.

Buying outright is another case , You may qualify for educational discounts along the way or non profit org offers.