I am going to throw out some possibilities.

A lot of your cost savings come from simplified design and leaving stuff out.  You also need to think long and hard about simplifying and  optimizing the build for a small crew.

First, it is cheapest to build a rectangle.   Think 28X40 or 32X40.   4 straight 8’ tall walls.    Skip the bonus space in the second floor.  This eliminates a stairway and makes the floorplan work easier.    This also allows you to use trusses for the roof which saves more money.   3 people can put up a 28-32 ft truss with some effort without a crane.  If you use a scissor truss, it gives you a  vaulted ceiling without adding much more money.  I like  5/12 pitch roofs which gives you a 2.5/ 12 ceiling pitch.  This gives you an 11 ½ ft high center ceiling in a 32 ft wide house  Specifying an 4-7” energy heal allows more room and insulation in the ceiling.   Make sure the house has 2 ft overhangs all around and orient the long axis of the house to face south.

5/12 pitch is plenty for a roof to have good water shedding, but is easily walkable and you can roof it without roofing jacks.  Don’t screw up a good roof with shed dormers, and other decorative crap.  Just makes roofing harder and gives you more places for the roof to leak

The second thing this does is make all the load bearing for the roof on the outside walls and simplifies floorplans as there are no interior load bearing walls.

 There are only 2 of you, so a single bathroom is fine.  Make the bathroom and kitchen back up to each other so you minimize plumbing.  This can save a fair amount of money and you can get by with one plumbing vent stack= less penetrations in the roof 

Eliminate hallways if possible, they are wasted space.

Use good ceiling fans.

Use casement windows.  They seal better and you get twice the open area of a double hung for ventilation

Spend the money you save on window upgrades, a solar water heater, and better insulation.

In the basement, if you are using ICF, pour 9’  walls.    This does not add much cost.  Bring the stone level with the top of the footings, put down a vapor barrier, add 2” XPS and pour on top of that.  Now you have an insulated basement with a net of 8’7” headroom and no thermal gap at the footing.   This works as a shop or can be finished off as living space.  You can run ductwork and still net a ~8’ ceiling in the basement.

The last thing is if you are building it yourself, it will go slower so account for that.  The subfloor and sheathing will get wet so use zip panels for wall and roof sheathing and use Advantech for the flooring.  They seem to hold up better to weather them most plywood and OSB.

Good Luck ,

Have fun

Eric Anderson