Hi, I heard that one may not benefit from meat and milk that were cooked together. I have a job opportunity managing a branch of McDonalds. Is this considered benefitting from meat and milk? Thank you.

Hi!
This is indeed a very interesting question. The Gemara (חולין קטו) tells us that there are three separate prohibitions that relate to a forbidden mixture of meat and milk. One of these is indeed a prohibition to have benefit from such a mixture. However, this prohibition is only relevant to a mixture of meat and milk which are forbidden biblically, but not to a mixture which is only prohibited rabbinicaly.
The biblical prohibition extends only to meat from domesticated animals, which were cooked or baked together with milk. Meat from a non-domesticated animal, such as venison, or the flesh of foul, do not fall under the biblical prohibition. Additionally, the biblical prohibition only applies to a mixture which was cooked together, if it was merely mixed after the cooking process, and not while on the fire, the mixture is only prohibited rabbinicaly.
The Rama (יו”ד פח:א) rules that one may derive benefit from a rabbinicaly prohibited mixture of meat and milk. This suggests an interesting leniency in regard to working at a non-kosher restaurant. If the cheese is only added to the burgers after they are grilled, then one is merely deriving benefit from a rabbinicaly prohibited mixture of meat and milk. From this article it would seem that the cheese in a cheese burger from McDonalds is never actually cooked with the meat. Therefore, one would be permitted to work at a McDonalds.

Additionally, the worker at a McDonalds is not deriving his salary directly form the sale of forbidden foods. The salary is set and paid from the company directly. Therefore, even if the cheese was being cooked with the meat, one would be permitted to work in McDonalds, provided they do not do the actual cooking of the cheeseburgers.

All the best