Lot of good points already, but one that I've learned the hard way is never take on a "family" business as a client. You know the type of company where one brother is the CEO, another brother is the marketing director, random husbands and wives work for the company, etc.
I've never had a relationship with a family business last beyond the scope of the initial project. Things always fall apart because of family infighting, or because every business decision ends up being way too personal/emotional for them. It's never worth the hassle, trust me.
45% of my clients are family businesses. That's a huge segment of the market to ignore (at your own peril). Family businesses can be great because they can be honest with each other, and move quickly. They can also be insane, but so can normal clients. I've worked with over a hundred family owned, multi-generational businesses.
I've never had a relationship with a family business last beyond the scope of the initial project. Things always fall apart because of family infighting, or because every business decision ends up being way too personal/emotional for them. It's never worth the hassle, trust me.