I have three minis, if you count my donk as one. I like the donk, but adore my mini horses. I’ve had several over the years. Some are little demons but I love my three little geldings. Even my little mini mare with wry nose syndrome was pretty sweet for a little drama queen. I lost her to hyperlipidema which is a concern coupled with trying to restrict their diet. They really must eat; not necessarily grass, but do not withhold food. Just less carbs and sugar. They also can be prone to dental issues and one gelding had a real time kicking a sinus infection.
Other than that though, they are adorable, sweet, cute as the dickens and entertaining. Mine have their own paddock but I have put them in with a lonely youngster or adult for company. You do have to be careful about larger pasturemates. Young colts that like to roughhouse are not a good choice. The mini, to make up for the size difference will stand on their hindlegs and if pushed back and down by the bigger horse, can rupture their Achilles tendon.
I’ve not had any trouble keeping mine in. They are smart and so if your fencing is not great, they will exploit that. They love to rub their bums on my wire fencing. I could stop that with a hot wire along the inside of their fence appropriate to their size/height. My smallest who is just 29" can walk through the V-shaped pass through in the four board fencing and lets himself in an out of the pasture with my big geldings if I’ve given them the run of the barn area.
All of mine have great feet and don’t seem to require as frequent trimming, but yes, otherwise, their care is the same as a full sized horse. Feed costs are very low. My three get just handfuls twice a day; some hay but not much pasture.
I’ve had a couple of mini foals and picking up a baby horse is your arms is pret-ty awesome. My smallest gelding has also been to school on pet day and was a huge hit. I could easily turn him into a therapy mini and take him to hospitals and nursing homes. He’s that chill. They love visitors and my nieces and nephews have all loved coming out and petting the minis as small children. They do great at pulling carts; riding - eh, not so much. They may be horses, but the attitude really is all pony. My daughter had a few to ride when she was small and gutsy kids do quite well; passive or timid kids, not so much. My daughter was more the latter so it was frustrating. So she moved up to a bigger pony pretty quickly. I will probably always have a couple personally.