I second a lot of what ShoeLady said about writing - even if you know your stuff and produce good output, because of the sheer amount of people who want to do the job, employers are going to reckon they can get away with making junior staff do it for less pay and get the same result (or a result 'that does the job').
What I've found is: plenty of places will be happy for you to work for free, so portfolio is not a problem BUT unless you market yourself as a personality, or are related to someone, the big bucks might seem hard to come by.
A related problem is: because of the apparent lack of opportunities, you can also become too afraid to leave the job you get, even if you know you're in a rut and it's time to launch out. So it's easy to stall in your upward climb for all sorts of reasons - as soon as you can afford a roof over your head, you don't want to imperil the regular income. It might seem glamorous to be a starving writer when you're 19 or 23, but if you're in your 30's, there is a whole other world of considerations (and social judgements) that you'll have to battle against if you do something irregular, like leave that steady journo job, to get back on the trail of your 'exciting career'.
Yet however hard it looks, overcoming the seeming difficulties is rewarding - even if it doesn't seem so, when you're standing in front of them, and can't see the way forward or around a problem.