This has been my first year as a beek. I too started with a TBH. I also have 4 Langs now. I would suggest that you go ahead and build more than one TBHhive, if you can scrape the wood together. If you ask around, you may find someone with wood lying around that they would give you. (I did) Build more than one hive so that you have the option of catching a swarm. When word spreads that you keep bees, you may get a call or two to catch a swarm. Fun stuff. You need to have a home ready for them.
It will be good for you to run two hives. You can compare them to see problems sooner. Also, if one starts failing, you have another hive to help strengthen it.
I would also suggest building a smaller box to catch swarms, if you want "free" bees. A friend built a 2-foot long TBH for catching swarms. We could take the swarm to a hive and dump them in. In one case, he left a swarm in the box for a couple of weeks. They built out good comb. He then transferred the good comb bars from the short box, to a full size hive. Worked great. Cheap. Good luck. Have fun.