If I work only half year does this affect my taxable income in eyes of SARS or maybe my tax rebate?

You are still taxed on your income for a full year regardless of having worked half a year. If your income exceeds the total amount for the 2014 tax year being R67 111 then you begin paying tax. However due to the way the monthly PAYE is calculated each month you are probably due a refund when you file.