Financing a new garage

When I bought our house a little over three years ago, I knew that it would need a new garage and soon. Our current 1 1/2 car garage is situated poorly on the lot, has a bad foundation, siding, electrical, roof, and door frame. It really has no redeeming qualities, as it is literally rotting from the ground up, and the frame is warped. Our garage can easily be classified as an eyesore, especially since it sits within four feet of the curb. Our goal was to build a new garage within a few years of moving in... ideally a two-story, two-car garage, with room for Mr. Savvy to have his Man Room (deer heads, poker table, etc.) in the upper level. Unfortunately, our garage fund was spent on windows last year ($10,000), and we haven't had much luck building it back up since. We don't have any estimates yet, but I'm thinking that we can expect a new garage to set us back at least $25,000, possibly quite a bit more. So, we have almost no cash to finance this new garage, and we already have two mortgages. What are our options? The first one is obviously to wait until we have the money, but that can take a long time. A second option is to take out an additional mortgage or HELOC. I don't want to refinance our first or second mortgages because our interest rates are very favorable (5.375 and 6.125), and it will be difficult to get a HELOC for the amount we need prior to building because we don't have that much equity at this point. A third option, which is less conventional than the other two, is to use the cash from 0% balance transfers to build the garage, with a HELOC as a backup. We could refinance our currently untapped HELOC after the garage is built (with our new appraised value increasing our equity), as a backup should the 0% deals dry up or in case we needed to pay them back on short notice. We aren't in a hurry at this point, but neither do we want to wait. A new garage would make a dramatic difference in our property value, which is a slight negative because we aren't planning to sell anytime soon and our property taxes will go up. The flip side is that Wisconsin winters aren't much fun without a garage to keep our cars in. Mr. Savvy is also excited to get his Man Room above the garage. My next step is to get a property survey done and then to try to get some estimates on what the garage will actually cost. Until then, we need to decide how much, and what type of, debt we are comfortable with. I'd be interested to hear about anyone else's experiences with financing home improvement projects. I'd also like to know if anyone has used 0% BTs this way before.