Have you thought of designing the guild to be a 'soup kitchen' ; that might offer a more life-like structure?
Hehehe.. Soup Kitchen - that would be a classic guild name.
However, the kind of image I had of this guild when Siofra first mentioned she was thinking about it, did not only include cripples, so to speak. It was also the street-kid type. Or general homless people.. not necessarily all destitute or hopeless.
Streeties tend to steal, use the community, go for freebies.. but also draw on other resources from their previous lives: savings, suckers in the family, a bit of mining when they can be bothered picking up a rockpick. Whatever comes with the trade too.. running messages, spying, knowing things, etc.
As far as beggars are concerned, obviously the leader of a guild like this would have to communicate with previous related groups and see if they wanted to unite or stay seperate. If they're not interested I think it's not a big issue, as it would only be a small part and others might come along and fill the role anyway. I think "how to beg and if to beg" should be discussed in another thread. It's certainly allowed. Anyway, it's not very important to this guild concept. Go elsewhere with that.