I have a T8 and ventilation is a problem unless you drill extra holes. And substrate like coco fiber and cypress mulch will give you lots of humidity, like dripping wet on the hides and things. Some keepers don't mind because the humidity will go down but it will take several days, or longer, due to lack of holes for ventilation. Scale rot occurs with bacterial growth on wet substrate and feces/urine which can take awhile to accumulate so spot cleaning daily helps prevent it. Imo fungi is the bigger threat but that too depends on what you have inside the enclosure to allow such growth. Personally, I prefer a dry tank over a wet one so I used aspen with a large water bowl. It is whatever that works for you and your snake.
When you are picking out your snake, make sure to ask if it ate, what type of prey, live or f/t, when it last ate, how many times and when it was last shed. There are breeders out there selling babies that had not eaten yet so while they may eat, it is better to avoid them as a beginner. Those who already have the experience working with picky eaters are more suitable for snakes like that.
Check for any mucous around the nose and mouth. Feel for any bumps from head to the tip of the tail. It would be loud around you but try to listen for any clicking or odd noises as it breathes.
A good seller is someone who would spend the time answering your questions or even offer additional info without asking. If he or she is getting impatient with you because you want to know when it last ate, skip that vendor. If they don't know something and they are not the breeder, they should be transparent about it and tell you that they don't know. Try to avoid the third party suppliers who are more concerned about making a sale. If something sounds too good to be true (Ie Really low price for a usually expensive morph), it probably is.
I had a great experience with Dynasty Reptiles if you come across them at the expo.
Be patient. Don't appear desperate or impatient. Take your time to pick out a healthy snake from a good breeder. If you don't feel comfortable who you are buying it from, skip them. While one can still buy from them and still do just fine, you want your first experience to be a great one, not one to start with worries and potential problems.