Not to concered about how to build the house, got that covered.
Some Tools I would need,,,,,going to need them sometime anyway.
I was more interested on how you drew up your plans, and figured out your house would cost.
I used Autocad 2000. I took a few weeks to learn the program and then started designing. Tip- You can never have to many closets. Coat closets, vacuum closets, dressing closets, and a walk in pantry. Yout wife will love you for them. lol Also, don't skimp on hallway width. Mine are 4' and it's nice. Same with my staircase.
Figuring cost is all leg work for accuracy. I used the 3 bid rule. I didn't have time to get 10 different bids on the work I contracted out, which wasn't alot but some. Some folks use a Sq. footage number but that will vary from area to area and it will vary by how much work you do yourself. Some things will have to be subbed out. You simply won'y have time. The bank won't give you forever. Probably a year tops.