Do you agree to hang billboards on the first floor of residential buildings and on the second floor? What does the law say?

No, the facade of the building is owned by all owners of the building, and putting up billboards requires the consent of the whole owner.

The Property Law stipulates that:

Article 72 The owner shall enjoy the rights and undertake the obligations for the part other than the exclusive part of the building; Never give up your rights and fail to perform your obligations.

article 73 roads within a building division are owned by the owner, except those belonging to town roads. The green space within the building division belongs to the owner, except for the urban public green space or the express individual. Other public * * * places, public facilities and property services in the building division belong to the owner.

Extended information:

In addition to the consent of the owner on the second floor, the following regulations must be observed:

Regulations on the Administration of City Appearance and Environmental Sanitation

Chapter II Article 11: Outdoor advertisements, placards, galleries, windows, etc. should be set up in cities with healthy contents and beautiful appearance, and should be regularly maintained, decorated or removed. The establishment of large-scale outdoor advertisements must obtain the consent of the administrative department of city appearance and environmental sanitation of the people's government of the city, and go through the examination and approval procedures in accordance with the relevant provisions.

chapter iv article 36: anyone who commits any of the following acts shall be ordered by the administrative department of city appearance and environmental sanitation of the city people's government or the unit entrusted by it to stop the illegal act, clean up, dismantle or take other remedial measures within a time limit, and may be fined:

(1) setting up large-scale outdoor advertisements without the consent of the administrative department of city appearance and environmental sanitation of the city people's government, which affects the city appearance.

References: Baidu Encyclopedia-People's Republic of China and Property Law of China.