I can totally see what you are saying about 'Paying it Forward' and often, I do it without even thinking.

For example, if someone gives me something that will help me out in some way, when I finally replace it or have no further use for it, as long as it is still usable, I will make sure that I pass it on for free as well. In other words, I don't sell or expect favours from an exchange of something I received for free in the first place.Anything given to me when either of my children were born, I also gave away for free when they no longer needed it.

However, there is one exemption in my opinion. If someone gave me something for free because it needed repair or didn't work and I invest any significant time and money into fixing it or restoring it, then I will probably decide on a fair price when I no longer need or want that item.Say, restoring an old car or repairing a broken computer as good examples.