This is sort of a simplification, but the further west you get in the Hill Country, the cheaper the land. Land close to Austin, or Fredericksburg, is super-expensive, they charge by the square foot, even for ranches. but you get further out it starts to get affordable again. I've seen land out in the western part of the Hill Country list for the low $2000s per acre, but I'd say median price is about mid $5000s. A lot of the price difference depends of water frontage. Also the further west-northwest, the lower the humidity. Junction, Texas, which is about the northwest extreme of the Hill Country, gets its highest humidity in August at around 50%.
As for taxes, Texas has no state income tax, only property taxes. With an ag exemption you'd save substantially on that. For instance, if you had 100 acres of land valued at $5,000 per acre, your normal annual tax bill would be something like $11,200, but with an ag exemption you'd only pay about $230. A zoo would not qualify you for an ag exemption, but if you were breeding and selling some of your livestock every year, that would qualify you for one. You'd have a ready market for them on the hunting ranches in the area. The other tax option, if you don't want to be selling animals that will end up a trophy in someone's living room, or you don't think you can meet the ranching production intensity that is common in the area (a requirement for an ag exemption) is a Texas Wildlife Exemption. You get the same tax break a farmer or rancher would, but don't have to farm or ranch. You have to first get approved for an ag exemption to qualify for a wildlife exemption, but what you could do is spend your first few years doing some breeding, that would help generate some capital for your venture, too, while it's still small, so you still have free land available for more intensive breeding, and then once you get the ag exemption, then the wildlife exemption, you could cut back on the breeding, devote that land to more exhibits, and still keep the exemption. The catch is you'd have to make sure your land provided habitat for
native species as well as your exotics, and those natives would have to have a human use, even if it's just recreation. But even butterflies are qualifying wildlife, and you could include some talk of native wildlife in your educational program. Heck, out where you would be, is part of pronghorn's historic range. You could purchase some and breed/exhibit them on your property, which would be a neat addition to your exotics. Here's some more info on that:
https://bjgnapvxtx-flywheel.netdna-ssl.com/wp-content/uploads/2015/03/96-354.pdf
As far as ease of living, there are a lot of cute small towns with good services in the area, it's not like some parts of the American Southwest where you're just miles and miles and miles from anything. And you're not that far of a drive from big cities like Austin and San Antonio.
You could definitely grow some more cold-hardy tropical plants, as most of the area is in USDA hardiness zone 8a, and ginger, elephant ears, canna lillies, mediterranean fan palm, even some bananas etc would all work there, as long as you watered them. But don't discount the natural scenery either. This isn't the Texas you see in Westerns (most of which weren't actually filmed in Texas), it's not dusty and tumbleweeds. It's lots of limestone hills and bluffs, with savannah-like open woodland of oak, cedar, and some mesquite. Really, when I traveled in northern Tanzania, places like Ngorongoro Crater, Serengeti National Park, Tarangire National Park, etc. really reminded me of the Texas Hill Country.
