What is the ruling of " Misyar Marriage " and what are the conditions of a correct marriage?
Can this marriage take place at a lawyer's office , or should it be done with a Mazun?

The word "misyar" is not a formal Arabic word but a colloquial word common in some countries. The word "misyar" may mean to ‘stop by’ or ‘stay for a short time’. Therefore, it seems that "misyar" marriage is derived from this meaning, because in such a marriage, a husband visits his wife at irregular intervals and does not stay at her place for a long time. Misyar marriage is deemed valid if it meets the integrals and conditions of the marriage contract and so long as there is nothing to prevent the marriage.
The woman's waiving her right to expenses and her husband spending the night with her or either of them, does not render the marriage contract invalid. [It is important to] take into account that a woman in a misyar marriage is entitled to ask for her right to expenses and to having her husband spend the night with her whenever she wishes. A husband in this case must fulfill her wish as per the words of Allah the Almighty, " And if a woman fears from her husband contempt or evasion, there is no sin upon them if they make terms of settlement between them - and settlement is best. And present in [human] souls is stinginess. But if you do good and fear Allah - then indeed Allah is ever, with what you do, Acquainted." (Qur'an 4:128).
The mother of the believers, lady 'Aisha (may Allah be pleased with her) narrated the reason for the revelation of this noble verse. She said, "A man would keep a wife and become disinterested in her. So, she would tell him, ‘I release you from any rights concerning me/I relinquish my rights’, so this verse was revealed” (recorded by Bukhari).
Ibn 'Abbas (may Allah be pleased with them both) said, “Sawda Bint Zam'a (may Allah be pleased with her) feared that the Prophet (peace be upon him) might divorce her, so she told him, "Do not divorce me but keep me [as your wife] and give my day to 'Aisha." The Prophet (peace be upon him) complied. Consequently, Allah revealed His words, "There is no sin upon them if they make terms of settlement between them - and settlement is best' (recorded by al-Tirmidhi).
Misyar marriage is similar to a kind of marriage that prevailed in the past and was known as the “day marriage”. The luminary scholar al-Kamal Ibn al-Humam said in his book Fath al-Qadeer (vol.3, p.249), "There is no harm in marrying a woman and spending only the day with her without staying over."