I’ve never lived in this kind of country, but I’d think you should brush hog the scrub – the horses can’t eat it, it’s a fire hazard, and they’ll get scraped up trying to go through it. Leave the trees for shade.

If you brush hog it regularly, the debris will rot away and enrich the soil, and the stumps will disintegrate over time. Take the stumps as low to the ground as you can to prevent injuries to the horses. It’ll be dusty, but useable as an exercise lot, which is probably the best you can hope for.

The downhill slope won’t hurt, and neither will most unevennesses, but if there’s a crevice or other spot they can really hurt themselves on, either fix it or fence it off.

I don’t think you can inexpensively get grass to grow without irrigation, but that’s beyond my knowledge.

If you get enough rain to grow forage, find out what’s best in that area of the country and seed it. Don’t put horses on it for at least 6 months, so the roots have time to establish.

Good Luck.

Fence it safely. There is not much you can do to grow grass on that type of land, unless you can irrigate. As long as you watch for sand consumption and provide good quality feed not eaten off the bare ground, and plenty of water, the terrain itself will not hurt them. Actually, uneven terrain and footing is good at helping a horse get fit and learn to handle themselves. You are not going to be able to get this property looking like a Kentucky horse farm, but that does not mean that you can’t keep horses there safely and successfully.