I dunno, when is someone ready?
where you ready for mushrooms or acid the first time you tried it?
I know i sure wasn't, i didn't even know what mushrooms were, i just ate them (almost a gram of dried ones) without having a clue what they did, i was almost 15 and clueless, the deraler where i bought my weed had two huge bags full of them but didn't warn me or anything, i just thought they where like eating spacecake.
Well, i kinda underestimated it

, first it was bliss, but when it didn't stop after a few hours i really thought i was going to be hospitalized for life, i didn't even know what psychedelics were back then, i heard of LSD but i had no idea what it did, but i wasn't ready.
Sorry, on topic again; if you tell him carefully what DMT is and what he can expect he can prepare himself for the ride, that way he will be ready, start with a low dose like our beloved Antrocles sugested and he'll be fine.
Although, i think a low dose will probably not give him a real psychedelic experience, but he can upper the dose after his first try to go a little further.