In sociology, researchers often speak of resources and analysing the exchange of resources between people. In the context of this study however I will treat resources in the traditional way as assets which you have that allow you to do things, or allow you to do things better. Thus items like services or love is not a resource, but things like time, network or money are.
Time is a key resource and specifically available in adolescence and retirement, and scarce in the time 30-60. It is simply the determining driver of how many friendship enhancing activities you can do.
Money is also a controversial item, and much has been written about ethics on involving money and friends. However it is essentially an enabler. With money, you can travel to visit friends. You generally have a different access to society. On the contrary, without it, not being able e.g. to join friends for dinner at a restaurant is inhibiting.
Network is likewise a resource. A large network introduces you to a lot of people, and you can draw your friends from it, as well as help passions of your friends by connecting them to like minded people (e.g. if a friend of yours is really into chinese ceramics, and you can introduce her/him to another person with the same passion, that is a great service you can do to your friends).
Health is also a great enabler. Or rather the absence of health is a great inhibitor. Of course there are many inspirational stories of people who despite ill health have rich social lives, but on the whole good health enables trips, sports activities, energy to go out etc.
Proximity is also an enable. Simply living round the corner lowers the threshold of having a coffee spontaneously, or dropping by to help out. Kids in the neighbourhood or village play with other kids simply because they are nearby.
Material base is money’s little nephew. It is not being rich, but describes the existence of certain enables, whatever they might be culturally, for certain friends activities. This could be an apartment with a living room and a dining table. It could be the car in rural areas, or a garden with a grill. Not affluence, but basic enablers in particular for hosting.
This constitutes the grey enabler box in the Friendship framework