You can calculate the cost of heating fairly easily if you know your surface area, insulation values and convection flow (air exchanges). Total up all the geometries of the building's exterior surfaces based on their conductivity (inverse of insulation). This gives you the total conductivity. Then you can calculate the heat loss. Add to that the air exchange heat loss (doors opening, venting) to get the total heat loss. You'll also need to know the indoor goal temperature and outdoor temperature as it is a differential problem. Break that down by month. It is essentially the same problem as refrigeration - look up that for more details on heat load calculations.
Once you know your total rate of heat loss you know how much heat you must add to the building to keep it warm. Coupled with the cost of energy and efficiency of the heater this tells you how much it will cost to heat.
The big problem with your idea is that your building will have a very low thermal mass. That's going to make it very hard to keep heat without heating it continuously.
We have a very small house. We built it before the Tiny House Movement. Rather than being part of a fad it was simply what we could afford to build in time and money before winter set in. We are located in the mountains of northern central Vermont which is very much like the climate of Sweden. USDA Zone 3 on a good year. Our cottage is only 252 sq-ft but over 100,000 lbs of thermal mass within an insulating envelope. This makes it store heat very well and never freeze. Unlike most buildings we have no cellar or deep foundation since we're on rock. Rather we are on a floating pad that is keyed to but insulated from the mountain's ledge. We use about 0.75 cord of maple hardwood per year for heat - no other outside heat source. Given the mass of our cottage I would not want to put it on wheels.

But then, I also like where it is.
See:
http://SugarMtnFarm.com/cottage for photos of our place.