I don't necessarily agree with a foundation wall and cement floor
I think you should price it as a crawl space , basement without finished floor, basement with a finished floor and as a foundation with poured concrete floor.
but any option that involves concrete floor should have PEX tubing in the cement it is such a good way to heat for very little cost you heat up the cement and you have many tons of thermal mass to hold the heat you still have to do everything else you would do with a concrete floor just that for a few hundred dollars in tubing your running the heat through the part of the house you would never get warm otherwise.
cement floors are always hard on joints and to stand on hard to hit if you fall but at least if it is warm concrete from heating lines running through , it won't also be cold all the time.
when you have a building not heated , then you start heating it a lot of time the floor will start to sweat especially if you don't have insulation and vapor barrier under it , it will always be cold and no matter how warm you make the air it never really warms up the concrete floor.
I have stayed in older slab cabins in the winter , furnace can run all night the floor never gets warm and it often sweats because it was allowed to get down to freezing for days or weeks before we got there and started the heat.
my wifes office is a slab , they keep the temp up they sell propane but she always complains of it being cold that slab never warms up it even has carpet over it
if you move the slab down 6 feet into the ground it changes things you don't have frost at the floor , you stay cool but warmer than outside I take a laser thermometer if I start it the top of the cinder block wall where it is expose to the outside , we have snow right now the wall is 51.5* as I move it down the wall the temp climbs about a degree every 16 inches the floor in the middle of the room is 58.5 mid summer it won't get over 62 my house is more than 100 years old and the basement has no insulation but it shows this effect well.
if your slab is at or above grade it acts as a huge heat sink stealing heat from your room
you have to isolate it with insulation around the insides of your foundation wall and under the slab that gets expensive , concrete is expensive so a craw space with a vapor barrier and some gravel over the top then a wood sub floor puts the least expensive of all insulation between the ground and your floor , dead air space.
it used to be you vented a crawl space , now you seal them up and insulate the perimeter.
knotty pine looks nice , but the cost is more than double even a basement board drywall that handles moisture and temperature swings better.
how about running water and septic will this have water and septic , how will you run that , where will the water shutoff be . how will you drain the house if your not heating it , what kind of water heater , will you be draining it every use of the house ?
America only has one issue, we have a Responsibility crisis and everything else stems from it.