Do you have a lot of humidity in your barn? It might be barn siding bugs I don't recall the technical names for them. I'd put some type of shelak on the wood it might help control the pests
Price it out yourself, I'm going to be building a 30x50 with room in attic style trusses for an apartment for myself to live in until my house is built.
Foundation 10-12k
trusses 8k
2x6x10 1k
sheething 1k
I am saving about 25k just to be safe
Sweat equity is were it's at