Pro Bono Work, the pros and cons

I've been thinking about this one for a while.  A good friend of a close family member asked me for some help recently.  They are just looking to focus their strategy, consolidate what they've got going for them and increase good quality sales.  It's a simple, straightforward local service business, nothing too mad or fancy about it.

Very kindly they offered to pay me for my services but I wouldn't hear of it.  When the close family member I know them through was having a tough time a few years ago, this person was there for them.  More than some other family members in fact.  I would love to be able to help her out now without having to worry her purse strings.  I believe that good things should come back to you. 

The freebie help was met with an interesting response.  I think I can understand why: she probably thinks that if there's nothing in it for me, then I won't put much effort into the project.  If I were to have some vested interest, I would drive more power into my efforts, perhaps.

I regret telling her I wouldn't take anything for the work now, not because I'm broke (which I am, GOD I'm so stupid), but because giving the goods away for free is going to devalue the work that I do.

DAMNIT. 

You see? This is why I haven't started up full time.  I NEVER TAKE MY OWN ADVICE.