Make sure you have a good support system. When we first bought horses 10 years ago, we had good friends that live about a mile down the road that were priceless with their advice and help. They had both grown up with horses and their knowledge was galaxies ahead of us.
Also, have a trailer just in case you need to get your horse to a vet, especially if you want to do rescue. I can't imagine NOT having a trailer. And with a trailer comes a pickup.....price of fuel - gas or diesel - is very high......
We have a barn with no stalls. If we need to put one of the horses by themselves, we have panels we set up in the barn for a temp stall. I don't believe in keeping horses in stalls.....they were meant to be outside, not standing in a stall all day. But the barn provides shelter in bad weather or when they want shade.
And before you ever buy or rescue a horse, do the math......how much hay will you need to buy, how much is it going to cost? Will you get it delivered or do you have to go pick it up and bring it home. Find out what your vet charges for routine stuff like dental work, shots and for more expensive things like house calls and x-rays. If you are really wanting to get into rescue, you really need to have a good relationship with a vet.
Find a farrier, get his costs. Are you going to have the horse shoed or leave it barefoot? You still have to trim! What about suppliments? Are you going to give grain or complete feed along with your hay? What about water? Do you have a trough? Automatic waterer? Do you have all the tack you need? Extra halters, leads, headstalls.....how about a saddle? Do you plan on riding Western or English? If you haven't ridden in a while, do you have someone you can go to for lessons (you might actually want to do this before you get your own horse) or a trainer that you can work with?
I hate to throw water on your dream, but these are all things that we learned AFTER we got our horses and things you need to consider now before you go buy one. It's been said before, if you can't afford all these things, you really shouldn't get a horse.
But if you can, good luck!
I love my horses and would really hate it if we had to get rid of them. They definitely make my life more wonderful than if they weren't in it.