Having a box in his garden can be a very good deal but a different story when it comes to finding a pasture close to the well being of the horse. Indeed, it is possible that you did not live in the countryside or even if you live there, the campaign in which you find yourself can not necessarily withstand rapid urbanization. The best would be to find you a green pasture for rent and settle nearby.
No estate agents
If you want your horse to be at ease in his new environment, you have absolutely no contact real estate agencies. Indeed, they are more interested in operations that have large and high value including building land or buildings. Also note that the agency you choose is not going to sell you surely farmland cheap especially if it is about to become a real building lot. However, in terms of rent, such land is often leased at reduced prices. Real estate agencies do not will be interested in such land with which they will not earn interest. However, you should know that farmers always have a high priority on individuals and that, as a tenant, you are going to benefit from a call option should the property that is leased will be on sale. The best way forward would be to contact the owners directly through the classifieds for example.
In a rural area
If you see a pasture made for your horse and used french saddles in rural areas, you can always ask to a local authority representative, references to its owner. This is usually one that has a minimum of conflict between the owners and that will totally help you avoiding putting the foot down. By contacting the owner of the pasture, you must also be very clear about your intentions to avoid misunderstandings.