Generally I do not recommend secondhand computers because you never know how much longer the hard drive will last. But a knowledgeable person can back up the hard drive so as not to have to worry about it. If the hard drive dies and was not adequately backed up, any software that came with the machine may be lost and you have to out and buy all new software including Windows.
First off you need to be able to turn it on and use it a little to at least be sure it has Windows on it with no password or the password already supplied. I strongly suggest it has at least Windows XP with service pack (group of updates) #2 (or something more advanced such as Windows 7 or Vista).
Half a megabyte of memory is workable but at least one megabyte is superior.
Also it should have a CD drive and you should bring a CD with some text documents or data on it to check if the CD drive works.
It should have at least one USB port, bring a thumb drive with some text documents to test that.
Use Notepad (usually still present within the Windows XP or Vista etc.) to get stuff off the CD and thumb drive to verify that those parts work.
If it does not have a wireless card built in you can buy a wireless adapter that plugs into a USB port. This costs about $50. from places like
Best Buy or Staples and you might choose to pass up that laptop rather than spend the extra money.
You will have to buy any additional software such as word processor or spreadsheet unless seasoned (well used, not trial edition) software of that kind is not already on the machine.