So also when the market is down to some extent, the person with $30 may likely loss more because of the money is small. Blockchain has the minimum amount one can invest if am not mistaken but if your amount is too small may be difficult to make easy progress.
What do you think about my advised to him?
Bitcoin never imposes any specific amount requirement on any user for investment. So a person can start investing in Bitcoin with any amount that can be $1 also. So $30 investment is not too bad or small amount to start investment. So you can definitely start investment from this amount but when you go to invest big amount then definitely recharge the market well to see if there is a big chance of bitcoin big dump at that time.