My advice regarding the saddle is wait until he is home so that you can measure his back. A poorly fitting saddle will irreversibly damage your horse. Speak with his current owners about tree size, and what kind of saddle he is accustomed to. You will also need to sit in a few saddles and see what fits your butt best.
As for off brand saddles... you just can't know unless you look at them in person. Mexico made could mean any number of things, but I like to stick with American made saddle. Rider's Choice makes a great, midprice saddle - perfect for a first saddle. They sell through ebay and are in Alabama.
You really, really, really need to know that the saddle you buy fits him. If you are buying used, talk to the person and ask if you can take it on a trial to see how it fits and return it if it doesn't. Whatever you do, DO NOT keep an ill-fitting saddle because it was expensive. You will end up costing yourself more in vet bills that way.