The statement of purpose for student visa (Visa SOP) is a document addressed to the immigration office explaining to them your purpose of study and why you should be granted permit to study in the country you are applying for.
Be specific about why you are applying for a student visa permit: You can explain that you have been offered admission by XXX University and also when you are expected to resume.
Create a link between your existing career and your proposed study: It is important that your course of study is related to your current profession and that you explain how the study will enhance your career.
Ties to home country: This can be in the form of family, business or property owned in home country or detailed plans to return to implement your study in your country; mostly non-severable ties to your country.
Proof of sufficient funds: You should be able to prove to the immigration that you have enough funds or a guaranteed means to support your studies in their country. Explain your financial background/income or other means to acquire enough funds to complete your studies.
Travel history: If you have traveled to other countries without breaking immigration regulations, this can be a significant benefit for you. This would assure the immigration office that you will leave the country upon completion of your studies.