OP, look in your area for second-hand Mazzer grinders. These days it’s really not hard to find something like a Super Jolly or Robur for a steal on Marketplace or other similar sites.
you'd be best to look for something second hand, like a Ditting bulk grinder. £600 new isn't going to buy you anything that will be happy grinding a kilo at a time. Burrs will overheat, coffee will be affected.
If he's roasting and wants to present a good product to the end customer, he needs to invest in a decent bulk grinder. You could look at second hand mazzer conicals also, like big roburs etc, they often sell super cheap on local marketplace sites.
Definitely get them to look at the used market. There are always loads of used Mazzer commercial grinders on the used market and they are built to last and will be within budget.
Nick_pj
