Jurors in Cook County Court returned a guilty verdict today in the unusual case of a man accused of stealing half a dozen houses. The basic facts were never in dispute: David Farr, who calls himself Javani Ali, took over vacant houses, mostly bank-owned, without permission. He lived in one and put tenants in the others. He said he believed himself to be operating within the law, based on his own reading. Jurors didn’t buy it. They deliberated for less than an hour. Sentencing will come later. The defendant had a partner who will be tried separately in October.