I wouldn't recommend buying secondhand from Joe Public. There are a lot of stolen laptops about. Also laptops not as robust as Desktop PCs. Any damage you discover after purchase may be too expensive to repair.
Look for at least a 3 month warranty, and operating system. Install Open Office. That should do for most note taking tasks. Hard Drive space is not curcial as long as you don't install loads of software and make do with Windows 98SE or ME.
Morgan Computers: click here