English teachers are in high demand in Mongolia although compared to British salaries, wages are low. Teachers can get working visas through the employer school and jobs are very easy to come by.
The bulk of jobs for foreigners will naturally be in the teaching industry. Due to the nature of the country, with so few areas urbanised, jobs in other sectors will be difficult to come by prior to arrival. Once in Mongolia, however, foreign bars and restaurants are obvious options. Any aptitude with the language will naturally be a huge advantage.