As everyone has said previously "there are too many variables to accuratel predict'". That being said, hopefully your builder won't scare the life out of you with his build cost, especially since you don't even know what his hourly rate is. A builder near me has a very reasonable rate of $48/hour.. His rate is lower than many. A finished car will run $30k to $50k depending on body style, motor, trans, paint, etc. The hotter, fancier, and prettier it is, look to doubling the range.

Actually I think you're a very lucky person to have someone like shawnlee28 to offer to assist with many of the little assemblies. It can save you a bundle. People with offers like that don't come along often.