Looking at your picture with the truck tracks it looks ready to use now ( but I'm flying a Maule
) there's not a piece of land that flat within a hundred miles or more from my place . Being a mostly retired dirt guy myself I'll only suggest heed your guy's recommendations for drainage.
I built my hangar ( farm building) as large as I could justify 40'deep x 60' gable & 12' ceiling and yes I wish I had built it bigger. I also orientated the bifold door in the gable end with clear polycarbonate panels to a southern exposure to gain maximum FREE solar heating in the winter months and maximum shading during the summer months. Insulated it well and rarely need to use the heater except on the coldest mornings or during several overcast days in a row.
Enjoy living what most can only dream of having your own aerodrome at home.