About age gaps

what do you think about age gap? i am 21 and chatting with this cute man of 36 . i like him for now and dont care about age gap . but i think at long term, when i'll be 30 he will be 50. how does 15 years matter? do you think is it possible to go for a relationship, or is it possible to only create a benefit-friendship?(maybe i should not think in long term too much, but i still do...)