Hi Alex, we here at 1304bikes also operate a completely volunteer earn-a-bike program. We are also completely run by volunteers, no paid staff. It is part of our goal to sell next to nothing. The only thing we charge money for currently is brand new cables (at $1 a peice), but we have so many good used cables, that we rarely even sell those. We like the fact that everyone can have equal and free access to our shop, parts and tools, and that everyone has to work to earn their bike. It is very important to us that folks with the privelage of having money can not buy their way out of working/volunteering for a bike. We are able to keep our money exchange to a bare minimum becuase we reside in a space where our rent is only $50 a month. It is not the most ideal space, but its cheap. We have about 400sqft of indoor shop and mostly storage, our bikes our stored outside in a temporary shelter, and most work activity happens outdoors.
So where do we get money from? Most of it comes from people giving us a few dollars here and there. We have also found that reminding folks about our donation jar during the clean up announcement usually nets us anywhere from $5-20 each time we're open. We try not to sell any bikes unless it is absolutely neccessary to make rent (and we haven't sold a bike in almost a year!). We have also decided at a recent meeting to potentially start selling nice parts. If nice parts end up with all the rest, they usually just get taken by the cherry pickers who can afford to pay for them anyway.
We would eventually like to move into a much bigger space because we are outgrowing our current one extremely fast, but this will most likely mean higher rent. We will then find ourselves in the same position you are in, of trying to find a way to make money for rent, etc. while still maintaining our ideals of an accessible and largely anti-capitalist shop.
Keep us updated on how things go, as this is an issue i think many of us are interested in and struggle with.
for 1304bikes, -Doug