Tang Qi's "my home" clearly wasn't referring to Thorns Campus.
After resolving the major event of the Evil God's descent, Tang Qi originally thought that the seals left by the Holy Confessor, Martin Sims, within the campus were almost all dealt with — first, a Desire Demon, and then the Evil God's Intestines; it felt like that was about it.
Who knew that, through the feedback of the keenly perceptive Little Guy, Night Beast, there was still the presence of the Power of Confession within the campus.
That is to say, there were other seals.
Faced with this situation, apart from Tang Qi sighing, "The old man sure has plenty of free time," his only choice was to shell out some Divine Grace Coins to buy the brick-and-stone building as a residence. In case he encountered an evil presence he couldn't handle in the future, he could still hide within the campus.