My only question would be is he going to be capable of doing a maths degree? I don't want to stereotype, but if he's made it to 40 and he's still working in a supermarket, well, why? Is it because he's not that intelligent, or did he just not care to leave? Maths is one of the hardest degrees you can do, so I'd hope he's capable if he's considering a decision like this. If he thinks he is, then yeah, definitely do it. That's a long life still ahead of him. I'm planning to do something similar, going to start saving up to go back to uni myself.