Just employ the chap properly, on PAYE.
If you’re at a stage where you can employ someone, then you should be earning enough that you can pay his pensions, employers NI and holidays.
No idea about apprentices, but let’s be honest; when people on here say ‘self employed’ they basically mean they want to pay someone cash on the hip. I’ll imagine there aren’t that many that have asked for an invoice from their ‘employee’.
Do it properly and don’t pay two bob and a conker and he’ll see it as a ‘proper’ job rather than a bit of beer money and you should soon see the reward in your bank balance.
(And while your ‘training’ him, make sure you work full days rather than slacking off at 1300 every other day or whatever. He’ll then recognise the expected work ethic so when he goes on his own its then normal)