Our chicken coop/run is about 6 feet from our garden. I made a "chunnel" for them that connects them to a large area at the end of the garden. It has a large forsythia bush in it that they use for shelter. In the winter I open up the fence and they free range in the entire garden to fertilize, till the soil and eat slug eggs.We're going to be using this modular Retriever Kennel from TSC as the framing for the run. After pricing it all out, that additional 10x10 area would cost us an extra $500 or so. Personally, I don't think that's bad, but I need to run it by my fiancé again. We both agreed that we'd be willing to sink a good amount of money into this, so I don't think he'll have an issue with it.
I'm so used to seeing my chickens in a nice big 30x20 space, but that is ultimately what got our first 4 girls killed. We didn't predator proof it properly due to the size of the run.