From Source, but say it is made with Source products?
Cause I would like to use Source models for my game and creating it.
Thanks! 
Only if they aren’t copyrighted. If they are in any source-based games made by Valve, then it is a definite no.
Well, it depends. Commercial use is probably out of the question, especially if you’re thinking of models made by Valve as opposed to some individual modeler. Noncommercial, you might get away with if you get the required permission.
So, I will need to contact Valve, ask them if I can use the models (Which people already do, fine examples are Black Mesa, Neotokyo, ect.) But I need to contact them regarding giving them credit, then also noncomercial use.
I just want to make a game from models in HL2 and Black Mesa.
Valve I doubt will say yes. When I wrote what I did about noncommercial, I was referring to independent, individual modelers. Stick with pivotraze’s answer when it comes to the legality of Valve’s property.
I’m not sure about Neotokyo, but the people who did Black Mesa made the models themselves. They look like Half Life’s models, but they were hand modeled by someone within their volunteer team.
You guys want to help with this game?
I just sent a message to Steam Support about this.
I hope to get a reply soon.
I am looking for anyone to help.
Most of the models will come from Black Mesa, NeoTokyo, and TF2
BTW: How do you open models in a game? I forgot 
Remembered. I will need a file type converter though
If you have to rip models from something, the original creator probably didn’t want you to have them in the first place. And Black Mesa is a source mod, using Source models and assets in Unity probably isn’t gonna work out. You’re better off learning to model, buying models, or getting some free ones that you can legally use. Turbosquid is a good site for free models, the Unity Asset store also has a lot of nice stuff too.