You can start a partnership, an LLC, or a corporation. But unless the law has changed recently, you have to have a Saudi partner. And you really need a Saudi counsel to make sure you don’t run afoul of the law. There are Western business practices that are not permitted, such as lending money at interest.

Foreigners wishing to conduct business in Saudi Arabia may do so in one of the following ways:

By establishing an incorporated entity
By entering into a partnership
By establishing a branch office
By establishing a representative office
By engaging a service agent