Aspen is the best shaving – don’t put pine in there, it causes respiratory issues. The recycled paper is fantastic, a little more expensive but the ultimate choice.
Has your brother considered getting 2x rats? Rats are naturally very social animals and group in family units. One rat will be lonely and depressed even with large amounts of human interaction.
Two rats are no additional work to care for, trust me.
PM if you would like rat care advice, I have had rats for years and a prominent rat club member.