Birches in general are found in cool, boreal forests, as a group they dislike heat. It is no surprise that they don't do well in Florida, or for that matter anywhere south of St. Louis. River Birch is touted as being more heat tolerant and insect tolerant than most of the other birch species, so it is sold all over the country. But I can see it having problems with heat in the southern tier of states. I would consider South Carolina a hot summer climate, unless you lived in the mountains. Definitely provide afternoon shade during the hottest months.
Birch as bonsai, I've seen a few images, and a couple local club member's attempts. They tend to be coarse, they don't ramify well. They look good as larger sized bonsai, somewhere over 2 feet, the best ones I've seen were around 3 to 4 feet tall. No reason not to try and use birch for bonsai, just take into account their natural growth habits into the design. (meaning go for larger sizes). Near me there is a river birch that was planted as a landscape tree less than 50 years ago. It is over 60 feet tall, with a trunk over 24 inches in diameter. The wonderful exfoliating orange & white bark is only on wood less than two decades old. It eventually develops an attractive dark, nearly black, alligator checked, and fissured bark. All good traits for bonsai.
Trees have open ended life spans, they don't expire at any particular point. One can always find individuals that are many times older than the Forestry Service stated life span. When the forestry Service states a tree's life span is 70 years, that is the age at which a planting of that species will have more than half the trees will have started to rot out their cores, rendering them useless for lumber harvest. Most trees can live another couple centuries with a hollowed out core, as long as a big wind doesn't take them out. So there is no "expiration date" for a tree. Softer wood trees loose structural integrity and begin to drop limbs and become susceptible to wind and storms sooner than hardwood trees. Probability of finding a multiple centuries old birch is much lower than finding a centuries old oak, but this is because their wood rots away easier, not because the living tissue quits growing. Vast majority of trees will live long enough to make a decent bonsai. So don't worry about a tree having a "short life span", that is not the issue. Now under my personal care, many a tree has a "short life span", but that is not the tree's fault, it is my lousy care.
Is the $ 14.99 tree a deal? It depends. If you view it as a test subject to practice and perfect your horticulture on, sure it is a good deal. If you really want a show worthy bonsai in less than 5 years of work, it is only a good deal if the roots where they join the trunk (nebari) and the first section of trunk are interesting. Since you will need to plan for a larger bonsai, the trunk should be over 3 inches in diameter, preferably 4 or 5 inches. If not it will take years to grow it up to that size. I would like to see 6 inches in diameter, but anything over 4 inches can look good on a 3 foot tall tree. Once you start to work the tree - it won't increase much in diameter, so it is best to start with a thick trunk, right from the get go. The $14.99 tree is no bargain if you have to grow it another decade to get something worth working on. Also if you have a choise, I would choose one without the broken branches. But if the one with broken branches is the one with the largest diameter trunk, only then would I consider that one.
Once you get it home, take eye level to the rim of the pot photos of all sides, post them and someone or many of us will give you ideas as to styling.
Hope my comment help. I would probably grab one, I really like the exfoliating orange bark on river birch. They are cool looking trees.
