ruben neves

should i buy him for 17 mil on 48 months?

Definetly, but keep in mind he plays best as regista, dpl or anchor man( but needs to improve on marking ability ). For a 17 y/o he has awesome mental abilities, you can train him for quickness, stamina or some technical ability,

£17m over 48 months...hhhmm...do people still use that old trick to affording players? IMO, yes the 'wonderkid' is worth a long term investment. he has been making waves at Porto IRL after surpassing Cristiano Ronaldo's youngest Portuguese ever to play in the champions league. he also scored on his first team debut.
he is blessed with some cracking stats at the beginning of the game and will make a good future international if you are playing a long term game.

back to your original query, it all depends on which team you are managing, finances, squad, etc. but £17m over 48 months is a pretty hefty commitment.