donations for local cong expenses are used to care for expenses incurred by the congregation INCLUDING the monthly rent or whatever you want to call the mandatory donation. as for assistance in building, every penny was collected before ground was broken, and every penny over X amount was requested to be donated, and was, at least here. now we can't even save enough money for seats that need replaced as the amount exceeds the operating allowance
there is never any accounting for where the money really goes, just vague references to "good use" you can trust them though