If you are in a poor country with a weak economy you could also benefit from joining a signature campaign. You won't be able to do it for about a 2-3 month period where you must show your contribution to the forums, but honestly that will probably end up earning you a lot more than mining with a single computer and you would also learn a lot more about crypto in general. Check the local boards if you speak a language other than English and you might be able to help there as well. Good luck.
No he can't join a signature campaign because he is a new user. There would be too many people spamming the entire forum it campaign managers took new members as sig posters. The signature campaign benefits the people who were around BTC for years. Basically if you were around since 2017-2018 and posted frequently and got your status to Hero or Lengendary then you can make decent profit for the amount of work you put in, however for a newbie member its not an option.
His best option is to get a low end RX 470 8GB and mine ethereum with it, currently ETH is rising and I think its like $1/day before electrical costs. With fees rising it will become even more profitable. If he likes it then he can start a large farm however the GPUs might be expensive in his country.