In the past I've had people I considered friends ask me to train them for free.

To which I say: Did you show up to work and put in eight hours for free?

So why would you then ask me to work for free? Someone you consider to be a friend should understand that this is what you do to keep a roof over your head and put food on the table. 

Do I ever consider giving a discount? Of course! It varies on a case by case basis but it's most certainly not the norm. 

Why does someone want to hire a trainer/coach? To save them time. 

All the information about training and nutrition is available at your fingertips thanks to the internet. By hiring a coach, you condense years of education and experience into a short term relationship. Hours poured into videos, textbooks and numerous injuries (which are one of the best learning opportunities, I mean if life gives you lemons you learn to make lemonade). You could sift through hours upon hours of information or you simply pay someone to distill it into a daily/weekly session. 

In my opinion, a friend should be someone who wants to support you. This person asking for free training is no friend of yours and doesn't respect what you do for a living. If YOU offer free training it's one thing (which I don't think you should do 99% of the time) it's another for someone to just straight out want it for free. NOT COOL!