(ה) ...כמה יהא בעיר ויהא כאנשי העיר, שנים עשר חדש. קנה בה בית דירה, הרי הוא כאנשי העיר מיד.
(5) ...How long must a person live in a city to be counted among the people of that city? Twelve months.
This part of the Mishna comes from a discussion about public works and their funding. The speaker here wants to know how long a person must live in a town before he is required to contribute money to the building or repair of a guard-house, a gate, or a city wall.
...וכמה יהא בעיר ויהא כאנשי העיר וכו': ורמינהי: החמרת והגמלת העוברת ממקום למקום, ולנה בתוכה, והודחה עמהן, הן בסקילה וממונן פלט. ואם נשתהו שם שלשים יום, הן בסייף וממונן אבד!
...How long must a person live in a city to be counted among the people of that city? Twelve months.
This conflicts [statement from another part of the Talmud]!:"If a caravan of donkeys or camels on its way from one place to another stays [in a "seduced city"] overnight, and goes astray with the population, the members of the caravan are condemned to be stoned [like any other idolators] but their property is left untouched; if, however, they have stayed there thirty days, they are condemned to death by the sword and their property is also destroyed [like that of the other residents of the "seduced city"]'
The editor of the Talmud notices that, according the laws of the "seduced city", it only takes 30 days for a person who was "just passing through" to share in the fate of the entire doomed community!
אמר רבא: לא קשיא! הא לבני מתא, הא ליתובי מתא.
ולכל מילי מי בעינן י"ב חדש!? והתניא "שלשים יום לתמחוי, שלשה חדשים לקופה , ששה לכסות, תשעה לקבורה, שנים עשר לפסי העיר.
אמר ר' אסי אמר ר' יוחנן כי תנן נמי מתניתין שנים עשר חדש לפסי העיר תנן:
Rava replied: There is no contradiction! [The full twelve months of residence] make a person a full member of the town, [30 days makes that person] only an inhabitant of the town...
...But is twelve months' residence required for all imposts?! Has it not been taught [in an earlier tradition]: '[A man must reside in a town] thirty days to become liable for contributing to the soup kitchen, three months for the charity box, six months for the clothing fund, nine months for the burial fund, and twelve months for contributing to the repair of the town walls'?
R. Assi replied in the name of R. Johanan: Our Mishnah also in specifying the period of twelve months was thinking of the repair of the town walls.