If he hasn't purchased MS Office, Excel would not be free; except for the 60 day free trial version pre-loaded on most PCs, but you still have to purchase the program to go beyond the free trial.
Linux user chiming in here. You can get Libre Office and Open Office for free. Personally, I use google docs; it's so much more convenient and I don't have to carry around a flash drive with all my stuff on it. On a side note, if I weren't so lazy, I'd make one and give it to y'all for a pretty dime.