I actually answered where you cross-posted on the western thread but what has been offered here rings true.
One stable hand around here (So California) costs me $22.50 an hour. That’s $15 (bare minimum for someone with any experience who will show up) plus all employment taxes and worker’s comp. Yep, for every dollar they earn, they cost me $1.50. You’ll need at least one stable hand full-time for every 20-30 horses, depending on stabling situation and what is expected in your area for board.
Sure, you can pay them cash under the table… but do you really want to risk a work-related injury and expensive-to-defend and likely-to-be-lost lawsuit against your entire lifestyle and security on that roll of the dice?
So don’t overlook how much your labor will add to your figures which will also include feed, bedding, facilities, maintenance, electricity, water, insurance, pest control, improvements, advertising, vehicles, equipment, vet and farrier… and your own horses adding not one dime of income to the mix, in fact they will be occupying stalls that could be at least making some contribution to costs.
It is VERY difficult to make money on boarding. Boarding is often priced unrealistically low relative to true operations costs because farms have been boarding for a long time and are legacy facilities that either have retired mortgages or other farm income or off-farm salaries which subsidize the boarding. It’s one thing to subsidize your own horses, but when you have to reach into your own bank account each month to subsidize each boarder’s horse out your window…makes one crabby!
Your place will need to be priced competitively with nearby legacy farms (unless you are in an area with no other barns at all) so competitor pricing can force you into a loss relative to your own costs just to get boarders in the door. No matter how snazzy your place is (and snazz is expensive) you can’t fill your barn without competitive pricing or a fabulous trainer… which is a whole 'nother kettle of fish.
Successful trainers don’t usually pay much of anything to work out of a facility (how nice to have zero rent overhead for your business, right?) but they need to be rainmakers to fill your (competitively priced yet also profitable) stalls. Someone who cares for horses and gives a few lessons is a different issue than a high-end show trainer, but any professional working from your place will need to be insured, get along with you and the boarders and their own clients, and not do things you don’t approve of to horses or clients.
You are proposing an expensive and complicated business that will require a huge expenditure of time, money, and energy to maintain. It’s risky. Talk to everyone you can find who is doing something similar in your area or riding specialty.
You may find that you love the lifestyle, that you and your wife are great at managing boarders and employees, and never even want to leave your fun stable.
But if not- it’s tricky to have an exit plan from such a complex business and lifestyle. And if you are finding nice facilities for sale… it’s not because their owners want to share their gold mines.
Just be business-like, not emotional, about your comprehensive business plan, financial realities, and all the reasons that the potential barn business is attractive. It’s very possible to build a retirement lifestyle that revolves around your passion for horses, but eyes-wide-open is critical.