Purchasing a used system is a tremendous gamble and we do not recommend it.   P3 warranties are non-transferable and thus you have no warranty.   You also may purchase a unit that is not working properly.  

You should also be sure the serial number is 10000 or above.   Units with a serial number under 10000 went End of Life on 6/30/2014.   They are not eligible for support or repairs.   Your only options are to perform a Serial-to-USB Upgrade (Contact Sales) or purchase a new package.