Well, a bigger tank may seem harder to take care of, but they are actually easier than small tanks. Try to make your friend get a 20gallon or bigger. Your friend will also need a good filter, i try to go for a filter rated for twice my tank size, so for a 20 gallon tank i would get a filter rated for 40 gallons. A water changer is also a must have. I would also suggest sand because IMO
it looks better and is easier to clean, if you have a gravel vac just hover about 1cm above the sand to get all the crud off. Your friend will also need a declorinator for when he does water changes. Finally, tell your friend to have fun, do lots of research, and tell him about this site.