Whether you should buy a return air ticket before applying for a visa depends on the specific requirements and policies of the country you are applying to, as well as the type of visa you are seeking. It is generally recommended to carefully review the visa application guidelines provided by the embassy or consulate of the destination country to determine their specific requirements regarding flight tickets.
In some cases, embassies or consulates may require applicants to provide proof of a round-trip or onward flight reservation as part of the visa application process. This is to demonstrate that you have a planned itinerary and intention to leave the country within the allowed timeframe of your visa. In such cases, you may need to purchase a refundable or flexible ticket, or provide a flight itinerary or reservation that shows your intended departure date.
However, in other cases, the embassy or consulate may not require a flight ticket or may specify alternative documents, such as a flight itinerary or a letter of invitation from a host, to support your visa application.
It is advisable to consult the specific visa requirements provided by the embassy or consulate or seek guidance from a visa application service or professional to understand the documentation requirements for your particular situation. This will help you ensure that you meet all the necessary requirements and provide the appropriate documentation for your visa application.