It does appear that Michael was a victim of foul play, his bank accounts haven't been touched and he didn't take his car or bike, and police have his mobile phone. He did cash building jobs and lived alone, he doesn't seem like he's mixed up in anything untoward like drugs. His old school mate David Benbow owns two properties with his estranged partner (they have 2 children) but was/is living with his mother. There could be a link about money or an affair? Police have identified him as a 'poi' and his properties are being searched.
Michael worked for cash which means there probably isn't a record of past and current jobs, there could be a problem if he was owed money or if a customer wasn't satisfied with his workmanship?