Sun beds will it affect me?

i want to use sunbeds before i go on holiday so a can get a real tan as am deathly white without fake tan. i very rarely go out in the sun. work all day and live in scotland so u don't see much anyway.lol. if a went to the sun beds for 2 or three weeks before my holiday then tanned on my holiday what will the affects be on my skin. is it only prolonged use that affects it.i am 23 so plenty of years out of the sun.will three weeks in it have any long term affects???