The display in the format you want is not possible (without much extra effort and the assumption that there are always as many locations as job categories).
However, with GROUP_CONCAT, you can return one row per user name containing all the information you are looking for, regardless of the number of job categories and locations.
SELECT users.id, users.username, GROUP_CONCAT(job.category) AS job_categories, GROUP_CONCAT(locations.location) AS locations FROM users INNER JOIN job ON users.username = job.username INNER JOIN locations ON job.username = locations.username GROUP BY users.id
The following results are returned:
5 Don Fashion/Design/Beauty,Eng,Arts/Audio/Video Technology Mr,Colombo,gm