How much money is needed to live in Sri Lanka for 4 months?

Hello guys. I am a student in the UK studying the second year of a computer science degree. My father is originally from Sri lanka and I have dual nationality which consist of the French and Sri Lankan and my mother language is French and I am fluent in English. I have been thinking to go there right after my exams in mid may in the hope of finding a work placement hopefully prior to go there, as a mobile developer focused on the android platform.

My main question is how much would I need in order to live there,considering that the accommodation expenses will not be needed as I will live at my grandmother's place down in Horana. Therefore the main expenses will be food for lunch time and bus fair probably from Horana to Colombo 5 days per week if I find my work placement in the capital. Lastly are summer placement usually paid in this specific field in Sri Lanka? I am not familiar with the country, therefore any answer would be really helpful.
Thank you in advance!

Asked by L.Ben via WorldNomads.com