How do you pick out someone as being homeless? I'm in the UK and (accepting in the US it may be different?) there is a common misconception that people who sit

How do you pick out someone as being homeless? I'm in the UK and (accepting in the US it may be different?) there is a common misconception that people who sit in shop doorways begging for money are 'homeless' people when, in fact, they are usually just people who have a drug habit they need to continually finance. The real homeless people are doing their best to blend into the background and not to look homeless. [I used to be such a person]