I have put a lot of thought into mine!!!
I would have around 100-150 acres of pasture... plus around 20 acres dedicated to facilities, stables, and yards. All my pastures would be fenced with very high quality fencing, probably what my boss has [3 strands, elastic, electrified... the horses don't test it and it's physically impossible to get hurt if they did get caught], plus one pasture for the foals [and of course their mothers] which would be fairly large, around 10-20 acres, and fenced with cyclone mesh [small diamond-shaped mesh, small enough for hooves not to get through, around 4' high with the top being one wooden rail per fence 'panel', a gap of about 15cm, then mesh to the ground and buried another 50cm underground]... foals can hit it and bounce off and won't get hurt.
I'd have a big barn, probably not heated as it doesn't get freezing freezing cold here but definitely with lights, and each stall would be a decent size [4m by 4m comes to mind] with a door to the indoor breezeway and a door to an outdoor yard... probably concrete then a good thick rubber mat to absorb some shock then pine shavings as bedding. Be around 20 of those, one for each of my 4 competition horses plus room for boarders.
BIG indoor, large enough to have a 60x60 jumping arena [bear in mind all measurements are in metres] and a 60x20 dressage arena plus about 10m between the two [unfenced, would use the portable plastic poles/markers for the dressage arena and then the same for the border of the jumping arena just without letter markers]. An outdoor dressage arena on good quality green turf, and an outdoor jumping arena on the same, each fenced the same as the pastures.
Two stallion yards for my stallions [top jumping-bred warmbloods of course!] which would be more like small pastures, plus two spare for boarders [facilities for stallions are woefully hard to find for those who don't own their own land]... very good quality 6' high fences utterly impossible to break out of or injure on, and the bottom strand high enough that the companion mini gelding could get in/out/under [border fence same as foal pasture to keep said mini in]. Miniatures make great companions for stallions so long as they have a way to escape if the stallion gets aggressive.
My house would be relatively small and cottage-y because I'm not into housework but would have a nice big kitchen with lots of bench space and storage... and a room dedicated solely to gaming with a HUGE flatscreen, a great gaming computer, and various consoles.
Adjoining the barn would be large lockable tack rooms - one for my stuff one for boarders - and a separate feed room so the mice weren't attracted to near the saddles... a barn cat or two, kept a little bit hungry because an overfed cat won't hunt. As well as an office for record-keeping, and for use as a show office.
BIG fancy cross country course going from bottom grade [here we have unofficial E grade which is only 18" and then the Equestrian Australia levels, and then FEI] to 4****... top quality showjumps with all sorts of kinds of fill, a course designer on-site, the best coaches in the country. In the outdoor [which on show day would become the warmup arena] would be the "work" jumps, more simple, and likely to be rather weathered considering they would live outside full-time.
I would have a prominent breeding operation breeding THE very best showjumping warmbloods in the country as well as wb/tb crosses, purebred TB's [using outside stallions for those, I have no interest in TB stallions] and anglo arabs [again using outside stallions], all for eventing... a band of maybe 20 broodmares roughly equal mix of warmblood and TB... and try for colour as well as quality because I have a big thing for dilutes and pintos!
I would only need, oh, a cool $30 million to set it up? And then a lot of money every year to keep it running... oh dear... better marry a mining mogul!