I would sell enough bitcoins to build a decent mining rig, say you sell 25 btc you can make that back in a month and then continue profiting. It is an investment, either you think it's worth it or you don't.
How can you mine 25(!) BTC with equipment worth ~500 USD that still needs to be shipped within 1 month?! This is BAD advice!Also, if you say: "But he can get 500 USD back, as the conversion rate increases if the difficulty goes up!" then I say: "If he does not 100% need this computer right now, he will make more then 500 USD by keeping the 25 BTC and selling them in 1 month!"
Paying Bitcoin to mine is a bad deal in very many cases. This is one of them!
You're probably right, I'm still a delusional noob most likely
It's up to him, if it were me I would probably sell some btc and build something, even if that's horrible advice. I could use a new computer anyway lol