I have to give to opposing view. I bought the 7-1/2 gallon pot and then a 10 gallon pot.
I now am fully into 1 gallon batches and the only pot I use is my 5 gallon.
I have a microwave about my stove, my 2 large pots are too tall and wont fit on my stove.
Before you over buy make sure it is what he will want to use in the future.
Some people do partial boil extract kits and are perfectly happy only going that far into it.