I’ve no idea if it would work where you are, nor even whether it’s really an idea that has legs, but an old boyfriend said there was money to be made in putting up polo ponies in the areas near to polo grounds - during the polo season, of course.
And the other thing that would work I guess is if you have a good network of bridleways, people might bring their horses for a riding holiday based at yours? The farm opposite us in Cumbria used to have a camping barn and some other economical self-catering, and some people would bring their horses for a riding holiday for them and the horses. Some based themselves there, and some were riding the Hadrian’s Wall coast to coast.