How much for just the garage, the rest of the property would in all honesty be surplus to requirements.
Private jets are more lucrative ( and safer ) https://www.motorcyclenews.com/news/2016/january/mcn-plus---micks-millions-what-doohan-did-next/
Does the yellow line represent the homebuilt racetrack out of interest, the only tricky bit that i can see is negotiating the water features.