So I helped the in-laws move into their new house. They have a HUGE yard, maybe around an acre or so. Next door to them is a small horse rescue. When I went over there, they had two minis and a large pony. I guess before that they had big horses back there. At first I thought they had a large yard but then realized that their back fence is actually the front yard to the in-law's new house. In fact, it isn't very big at all.

Curious because I have always wanted a horse but figured I needed a crap ton of room...by crap ton I mean a few acres.

You need at least 2 acres of pasture per horse.

you don't need that big if you aren't expecting them to get their food only from the grass in the yard. but it does need to be zoned so you could have one

I agree with the 2 acres per horse. We had a woman who wanted to keep her horses in our pasture temporarily. We thought she was bringing 2 but she brought 4. We have about 4 acres of fenced pasture and they had it eaten down to dust in just a short period of time [and that was in addition to giving them hay regularly]. Note: these pastures had not been grazed in years so they were very overgrown.

2 acres is a genera rule of thumb, and that is not for grazing, imo.

You would need much more acreage per horse (depending how amazing your pasture is) to graze.