He then studied law and later worked as a teacher in a small village in Hinigaran, Negros Occidental.

Along with his career as a lawyer, he also dedicated himself to teaching and became a faculty member of the Molo Institute, a Filipino school established by Ilonggo intelectuals.

Guanco feared this would lead to severe financial consequences, including the withdrawal of government funds and the cessation of credit from British banks due to World War I.

To address this, the farmers sent representatives, which include Guanco, to Manila and lobby for the immediate passage of the bill, recognizing its crucial role in supporting the agricultural sector in Negros.

[4] Upon the establishment of the Philippine Senate in 1916, he was elected as the first representative of the 8th senatorial district composed of the Negros provinces, Antique and Palawan.

He also became a member of the Senate committees on Agriculture and Natural Resources, Elections and Privileges, Finance, and Relations with the Sovereign Country.