I did the doors for 3 years and still have my SIA badge - knocked it on the head about 2 years ago.
Money is ok if you get a nice venue (i.e where there aren't smackheads trying to stab you with syringes in the toilets - as happened to me once...) - I was regularly taking home £150 a weekend for doing Friday, Saturday and Sunday nights.
Make sure you get in with a decent organisation who are all legit and above board and if they cover a few venues you shouldn't be short of work.
If you can remain cool, calm and collected when you've got some pisshead yelling in your face - you'll be fine. If you've got a short fuse, it can land you in trouble with the old bill sometimes