[originaltext]Social life in America varies tremendously from office to office.

Social life in America varies tremendously from office to office. Big corporations may have clubs, sports teams, trips, dance classes, or other employee activities which you can join or not as you like, while small companies usually can’ t afford these activities.
In general, people go to lunch with each other by invitation when they feel like it. Usually people of higher ranks would invite those of lower ranks rather than the other way around, but lines are not closely drawn. Except for special occasions, everyone pays for himself or herself regardless of whether or not an invitation is offered.
It is quite acceptable for men and women colleagues, single or married, to go out together for lunch. This may be the extent to which your office friends will invite you. Although in general Americans readily take people home with ,them, they often do not want to mix business and social life. If this is the case in your place of work, you will have to seek your friendships through other channels.