Does a SF rental have to meet current code in Texas?

[Marian Smith]

Texas Property Code states explicitly how many locks and fire alarms are required in rentals. But I don't see anything about bringing an older house up to code. Specifically, if the door from the garage to the house appears to be solid core and has not been replaced since the house was built in 1982, is that okay. Obviously it met code when the house was built, but I dont see a stamp or anything identifying it as fire rated. Thanks in advance. (and please dont advise to replace it just in case, which I may do with a metal door, I want to know if I am required to.)