Money is a strange beast. However professional we are or try to be, money can corrupt. Us and others. I don't claim to be unaffected by it, either. It is the very character of money. Due to this, our minds play havoc with the relationship and many times, a good relationship is soured due to this.
Some would argue that is is actually good to involve family or close friends in business because it is very good to have someone you can trust. That is really a call you have to make. Are you ready to risk spoiling the relationship?
The converse is also true. Never make someone you have a professional relationship with as close as family. Never get too close with someone you transact financially with. It can mess things up.
When you are paying for some services or products and the expectation is not met, you need to have the comfort to be able to talk about it. This comfort is compromised when you have a close relationship. It works the opposite way too. When you provide services or products in return for money and you have a grievance, it is difficult to air it with someone close.
I am writing this from experience and have seen both these aspects play out badly in the past.
... http://www.kamaldshah.com/2010/12/mixing-business-with-family.html
