I need advice about thoroughly cleaning a lazy college boy's bedroom.

So I’m in charge of cleaning my step-mothers house. Her oldest son almost 22 is away on vacation. I walked into his room earlier and had to walk right back out.

There are plates of moldy food, about 200 empty/not empty soda and beer cans and I don’t even want to know what is on the floor.

Besides the obvious take out the dishes and throw away the trash, what should I do?

It smells like death in there.