he doesn't have any financial investment licence from MAS to do what he is offering to you.

most importantly, you could be hauled to the SPF's SSB department for money laundering or money lending activities.

so in short, you are pretty stupid.

if he vanishes into thin air, which if you are familiar with the SG crypto community, there are such cases. you have zero legal recourse, meanwhile, he could be giving an interview to ST on how he managed to multiply his investment though it's through illegal means. Why? cause he won't be confessing that it was earned through illegal canvassing of funds.