Understanding water & soil are important. Learning about good land management is about learning to use the natural services & capacity to their fullest extent & there are lots of great pre-existing resources already out there, so if it’s not something you’re well-versed in, seek those out. Google is a good place to start. There are also great resources on this board & I am one of many who are happy to answer more specific questions as you get into the details.
Please, if you have natural water bodies on the property, protect them from livestock & runoff. I can’t overstate the importance of this.
The lower density of horses on a property the easier your management is, especially on smaller acreage. Carrying capacity of land will vary substantially with region, soils, grasses, as well as the fact that some horses are just harder on pastures than others. A fence-walker who loves to play galloping, skidding, extreme games will be harder on the land, even if smaller, than a chill critter who meanders quietly about & that can change how you manage. For example, I’ll let older horse who is very mellow in the pasture sooner after rain than I will the young one who likes to do a bunch of said galloping & skidding.
DO have sacrifice paddocks. This is one of the best things I did – even if you don’t have the luxury of designing the farm yourself from scratch, you can still add them. Quality modular electric fence systems have made this so much easier these days. And be willing to sacrifice them, it’s what they are for.
Horses don’t need stalls, they really don’t, 99% of the time. You & the horses will be happier allowing them to stay moving. Horses really are waterproof & really can produce their own body heat. This also allows you easier implementation of the final & most important rule –
And the biggest one: you don’t have to let a farm own you. I run my 10 acres by myself, but I do what I WANT to do first. That grass will always be there needing mowing later & whatever is broken (farm rule: something is ALWAYS broken) ain’t gonna fix itself, despite my fantasies, it will still be there too. If you are lucky enough to have a sound horse to get on right now, DO IT RIGHT NOW. And do it first before you get tired. My farm won’t win any Better Homes & Gardens awards & it would give a full-on heart attack to an HOA lawn dictator, but it’s full of amazing wildlife, the horses are happy, healthy (well, as much as being giant animals with a death wish ever can be), and safe & I am not a slave to dumb vegetation or aesthetics any more than I want to be (I work full time & before the virus, I traveled quite a bit for work).