Are you familiar with the musical “OKLAHOMA?” In it there is song that contains the lines:
We know we belong to the land,
But the land we belong to is grand!
I’d say that most folks who board (either their own horses or somebody else’s) would agree with this sentiment. But when the song says “belong” it means it! If you’ve managed a barn before then you know that. The mistake that folks make is charging too little for the service. They do that because their love for horses, and the land, drives them to undervalue the service they provide. If you don’t try and make a profit you won’t just lose a little, you’ll likely lose a lot. I personally know at least a half dozen folks who tried to do what you’re thinking of and got burned, and burned out, pretty quickly. The ones who stuck to it did it as a “labor of love” and didn’t care about the difference between expenses and earnings.
Do a “market survey” and ask operating barns in your area what they charge for various board types. While you’re doing this get out your yellow pad (or open up Excel) and start building spreadsheet on costs. Be sure to include such things as fencing, taxes, depreciation, and reserves for problems. These would be in addition to the standard stuff most folks think about. Make SURE you include labor. One thing you’ve not said is if your SO is “on board” with this project. Are they going to ride and care for their horse and be an active participant or is this you doing your thing and they will do theirs and help you out as they can? If it’s the latter item then your likelihood for success is reduced.
Your best bet in this situation might be to find someone looking for a facility to lease. You might be able to find a compatible trainer to run their small operation out of your stable. They would take over running the barn, including basic care for your horses for a rental fee. You can leave hiring barn help to them. Obviously,a really good contract spelling out duties, money, limitations and expectations would be essential.