so long as I was very clear in all advertising that I’m only building houses and not in any way related to the cars - but if I start putting Lamborghini cars in my advertising I could get into trouble for creating confusion

That’s fine. But suppose your brand is Lambozucchini and you have cars kinda similar to Lamborghini, but with the brand clearly different, just with homage, a bit like Pepsi-Cola and Coca-Cola, where in the world is the problem with that? That should be legal, from common sense.