What temp does the specific room get you're tarantula will be kept in?
If it's 70f during the day and drops a little at night most tarantulas will be perfectly fine. I use heat mats attached to thermostats on the back walls to keep mine warm as I don't use central heating so in winter and on colder days the room gets cold.
On hot days the mats don't even come on which is why you MUST always connect mats to stats.
Also once your main viv is up and running for your corn will heat up the room too. Best bet is to just get your corn set up and then see what you're dealing with.
I'd definitely pay a little more and buy a sexed female juvenile or young adult as your first tarantula.
Jack Torrance: Mr. Grady. You were the caretaker here. I recognize ya. I saw your picture in the newspapers. You, uh, chopped your wife and daughters up into little bits. And then you blew your brains out.
Grady: That's strange, sir. I don't have any recollection of that at all.