Wow, I wish I had 780,000 that place is gorgeous! I would say everything depends on your area. Then you are going to have to add everything together and figure out what to charge your borders and you are going to want to keep it reasonable or you aren't going to get any. Its a really hard thing, plus you may find that you are not going to have a full barn all the time which may cause you to up the board on the people already boarding there. And you are also going to have to pay for staff to run a facility that big. Riding instructors and stable hands and probably a stable manager and those start out at at least 12 and hour. Plus insurance, which I'm sure is not that cheap. It is a pretty costly thing, but if you can save money on buying a place you can put that extra money into everything else. Its kind of a gamble sometimes.
Every single place does not need to employ a riding coach. You could offer just board, and have outside coaches welcome. Just make sure that outside coaches have signed an appropriate waiver, obviously along with your boarders, to make sure that you are not liable for what happens to them.
This place is exactly the type of place I am looking for actually, except I would like at least 50 acres. The property FeatheredFeet showed as an example would probably go from anywhere around 300,000 to the price it is listed at depending on location in Southwestern Ontario....and only the lower price because it is lacking in acreage.