Left For Dead Characters

Question

Are the characters in Left For Dead 1 and 2 modeled after real-life people?

Answer 1

It depends on what you mean by "modeled after real-life people".

If you mean visually, then yes! Valve usually models the face of their characters based on some real-life person (probably a hired model or actor, but I can't confirm this). From Left4Dead Wikia, here is a list of the face models for each character (as well as the voice actor):

.------.-----------.-----------------.------------------.
| Game | Character | Face model      | Voice actor      |
|------|-----------|-----------------|------------------|
| L4D1 | Bill      | Bernard Fouquet | Jim French       |
| L4D1 | Francis   | Taylor Knox     | Vince Valenzuela |
| L4D1 | Louis     | Sean Bennett    | Earl Alexander   |
| L4D1 | Zoey      | Sonja Kinski    | Jen Taylor       |
|      |           |                 |                  |
| L4D2 | Coach     | Darnell Rice    | Chad Coleman     |
| L4D2 | Ellis     | Jesy McKinney   | Eric Ladin       |
| L4D2 | Nick      | Taymour Ghazi   | Hugh Dillon      |
| L4D2 | Rochelle  | Shanola Hampton | Rochelle Aytes   |
'------'-----------'-----------------'------------------'

The body is easier to model in 3D, and is probably based on sketches made by Valve artists. However, it is very difficult to accurately model a face, and that's why they use real-life models for faces. (but, of course, they fine-tune the modelled face to fit better to the character, like the G-Man from Half-Life series)

Answer 2

It appears that they are just stereotypes:

Wikipedia article

There are four playable human characters in the game: Francis, a stereotypical biker (voiced by Vince Valenzuela); Bill, a Vietnam Veteran (voiced by Jim French); Zoey, a university student (voiced by Jen Taylor); and Louis, a district Account Manager (voiced by Earl Alexander).

(my emphasis)

However, I wouldn't be surprised if each characters appearance wasn't based on a real-life person - but that person could be anyone, even one of the developers!