He could set up a multi million pound property company to purchase all his 'stuff' whilst paying himself £12,500 a year. He then leases his car/his home/clothes etc from the holding company at say a pound a month, which, on paper doesn't make a profit, ergo, no tax. Especially if the property company is based in Nassau.
Hypothetically speaking.
No, he can't.
His employer will be Manchester United, or possibly he's employed by "Marcus Rashford Ltd" and Manchester United pay the Ltd Co for his services - although that may fall foul of IR35.
If he's an employee of ManU then there is no way to avoid income tax and NI because ManU will have to pay it for him (PAYE). The income tax alone is almost £13.8 million p/a on a £500K p/w salary. Plus with employee NI and employers NI the take for HMRC is going to be circa £18 Million p/a.
If it's done through a ltd company - how on earth do you think a company can avoid making a profit when it's income is £26M p/a, and it's (employees) costs are £12.5K plus a few £K NI and pension? The corporation tax rate is only 19% - so a lot less than the income tax rate, but Marcus cannot extract the "retained profits" from the company without paying yet more tax.
And the idea that the company can buy cars and houses for you to live in 'for free' is also nonsense. It'll be treated as a benefit in kind by HMRC.