Not only mindset but the way of living. There is nothing worth noting that if someone wanted to change he needs to changes the way he do things. Mindset is just a generalized vague word. Let us say the person wanted to get out of poverty that is his plan and his mind is set on that plan. Doesn't change their mindset defeat their purpose of getting out of poverty? At most the best advice is to change his way of living. If he is lazy then be hard working. If he lacks knowledge then strive to learn. If he is shy then be confident. It is much better to list the things need to do than just saying vague stuff like changing your mindset.
To change their lifestyle, a person needs motivation. It is not uncommon for homeless people to enjoy their way of life. The ephemeral freedom, the independence from society, the ability to do anything - many of them find pleasure in it. They just get used to living in poverty - and don't even want to change anything. So it's the way of thinking that counts.