First things first, setting up for artificial insemination is expensive. A lot of places do it because it is safer for the stallions. That said its not usually a mom and pop thing. It use to be 15-20 years ago but now most people end up shipping their horse or stallion to the facility to cover mares. This could be a niche market if there is not a facility in the area; however, you have competent veterinarian on staff to collect the stallions and to store the sperm. Sperm are only viable for a few hours. Thus a lot of places collect Monday, Wednesday and Friday morning and ship out that afternoon in the hope that the sample arrives at the farm the next morning. God help you if your mare ovulates on Sunday.
The first tools they would need are whats called a phantom mare (a stand basically), an artificial vagina and an ultrasound possibly. This is the big cost items of the operation. Then they need a cryo tank to hold the semen and its a wise idea to have a microscope to make sure the sperm are viable.
The real issue is in training the stallions to the phantom mare. While fans of AI say that it makes the stallions much easier to handle. They associate the phantom mare with breeding and not a regular old mare. They would also need a teaser stallion to alert to when the mares are in heat. There is an art to training a stallion to the phantom.
If you start boarding mares to breed to the stallion using AI. You need to have a vet to ultrasound the mares to determine when they are going to ovulate or have ovulated. This is done by ultrasounding often every few days to everyday during the heat size. The doctor will measure the size of the follicules and the texture of the ovary. Once the mare has ovulated the follicule will be smushy feeling. To ultrasound a mare you are going in rectally with a probe and measuring. This means for some mares you need a stocks and for others you need a stock and a tranquilizer. Around the time of ovulation and ideally at ovulation to insert the semen. Most semen is frozen and shipped in two syringes. In theory, you get two "breedings" per shipment. That said its wise to check the semen before insertion into the mare because some studs are duds. Most places will ultrasound a few days to a few weeks after breeding to ensure that mares are in foal.
It can be expensive and if your friend is really interested in it for her ranch I would suggest she work with her local university or vet school. A lot of them will train the AI stallions. There is also an art to ultrasounding mares and reading ultrasounds which takes a lot of practice. Its something that before you dive into financially its best to spend a few weeks at a breeding facility.