I ran pubs in the West London area for a few years, I got out of it eventually as I couldn't take the long hours and crap pay.
Regardless of whether you go free house or managed, you'll work every hour of every day - my first pub, I was behind the bar from setup to close, every day, for a week. I was so scared of something happening and me not being there to deal with it, I didn't dare to leave the place.
Even when I got more confidence in running places, you're still tied to the pub 24/7. Your phone has to be on at all times when you're away, as inevitably something will go wrong whilst you're out. Even with a decent assistant/staff, you'll be chased if there's a problem.
Combine with the low wages (living on premises is nowhere near worth the drop in money you'll end up having to take and if you're freehouse, prepare to live permanently on the breadline) and the antisocial hours (forget seeing your mates at the evening and weekend), I just can't see why anyone would want to manage a pub.
And all that is assuming you get a decent pub with trustworthy staff who don't nick off you the second you turn your back and the punters aren't complete t**ts who wreck the place, take drugs and start fights every weekend. When I worked for Scottish and Newcastle, standard practice was to give new managers the s**thole pubs that no one else wanted to "break them in". Never knew anyone fresh in the job who got a decent first post.