This is almost important as the idea he has.
The Accountant will suggest a suitable program that it's house Staff are familiar with.
And the Important Bit - Will help him set it up so he is recording the right stuff.
Accountants usually charge nothing until the end of the first year of trading. They want your business, the more you make the more they make. If the business flies he will need an accountant to sort all that tax he will be paying, and if it bombs, to claim back whatever he can.
Otherwise a Cash Book can be purchased from John Menzies for 40p. The small trader round the corner may have it cheaper