Small mexican family (2 adults, 2 small kids) looks for two month economic residence in Montpellier (october-november 2019)

I don´t speak very good french, but I can read it and understand it a bit. My husband is going to Montpellier to share his master project with an organisation over there. We have a 5 year old daughter and a 2 year old boy. We are looking for an economic residente of about 400 euro a month, but near the center of the city. We would be in Montpellier october and november. We need to be back in Mexico City in december. If you know any good option for us, we would greatly appreciate it. We have only a few weeks.

María