Tell him it's too late to mine for bitcoin as the money you would pay for electricity alone will cause a huge net loss. If the electricity is free, then he would also need dedicated hardware, meaning something that was created for the sole purpose of mining bitcoin (ASIC mining). Your next best option would be some other crypto-currency. Ethereum is still possible, though won't be for long due to proof of stake. Litecoin, Dash, and XMR are possible too. Please look into mining as there are many estimator/calculator websites out there for you to gauge your profit margin.