To start off with, I came up with different rooms I would like to include in the cottage, aside from the necessary ones. Then, I drew a layout from the Bird's Eye View and fitted the rooms in with the dimensions. After that, I placed the windows and the doors and drew pictures of how it would look like from the front and the side.
After I was satisfied with my blueprints, I created a 3D version of it on Tinker Cad. I made exterior and interior walls using the rectangular prisms of different sizes and windows and doors using rectangular prism holes. I also made a roof for my cottage by using the triangular prism tool.
These are images showing different views of my 3D Tinker Cad cottage. I used the different perspectives to help me calculate the costs for painting the exterior walls, heating in the winter and putting shingles on the roof.