The Independent article that some of this links through to says:
After school, Breivik did a brief stint in the army, and then appears to have gone from one job to the next. He is believed to have started a computer company and earned enough money to live in a luxury apartment and sport a Breitling watch. However, other reports suggest that for years he worked in a lowly call centre and lived almost anonymously.
...
Exactly what he lived on in the run- up to the massacre remains a mystery. But his bank details reveal that in 2007, a sum equivalent to €80,000 (£70,000) was added to his account, which would have enabled him to live without having to work.
...
However, his personal and sexual life may well provide criminal psychiatrists with evidence to explain his warped personality, his clinically obsessive character and even the motive for his acts. One clue is likely to be his ailing mother: she has not spoken or been interviewed since the massacre took place. But if the closing pages of Breivik's manifesto are credible then her ailment appears to stem from the final stages of an unspecified venereal disease which he claims she contracted several years ago and has since reduced her mental state "to that of a 10-year-old".
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Neighbours described Wenche as elderly and frail, but added that she was a gregarious and welcoming woman who often chatted to strangers and was fascinated by foreigners. She remarried a Norwegian army major. But although apparently regarding his stepfather as a "good bloke", Breivik appears to have secretly detested him for being a product of permissive Norwegian attitudes to sex. He blames his stepfather for having infected his mother with venereal disease which was also passed on to one of his half-sisters.
http://www.independent.co.uk/news/world/europe/what-turned-anders-breivik-into-norways-worst-nightmare-2327214.html(that was written Thursday; if anyone's seen more up to date information, I'd be interested)
It's possible that if his mother's mental state is failing, then he's been getting the money out of her, I suppose. But his 'career' looks pretty patchy to have allowed him to spend so much time learning how to make large bombs, and that sudden €80,000 will be very suspicious if it wasn't from his mother.