Cost of excavating

where to start??? We have an unfinfished basement. We want to add a bathroom, laundry room, bed room and a family (rec) room. What do we do first? How do we plan where to put walls? Lots of ideas but have no idea where to begin! Help!

I live in Illinois where it's really humid in the summer. I can't afford to concrete my crawlspace so what I am planning on doing is laying 2 inch thick poly-styrofoam insulation panels all over the floor(to save my poor knees from the rocks and pipes when I have to crawl around down there to fix things) and walls for insulation value. I am currently in the process of putting up insulation on the floors, ducts, and pipes too. Then I was thinking ov covering it with tyvek for a vapor barrier. I will put furring strips on the walls of the crawlspace(which is about 4.5 feet deep) about 2 feet up to keep the very little seepage below. I was going to caulk or tape the seams of the tyvek to keep them from splitting apart when they are crawled on. Does anyone think this is a good idea to curtail the bugs and mustiness in the summer? I will eventually put in a fan, but I haven't gotten that far yet.