used the command you provided and can do sessions now.I don't know what to tell you.
Basic step to get the modelling job started is:
Search for a job on your phone 4 times and you'll find the photo studio advert asking for models.
Go to the downtown area and then to the photo studio and talk to the photographer.
Then in the character's (that are able to become models) request option there will be a option to ask that character to be your model.
The only time when I've ever had a error with the model job not unlocking is when I was skipping the dialogue with the ctrl key, so if you got the model job error then you have to start again without skipping the dialogue. Or go hunting for the variable that unlocks the modelling job.
Either way good luck.
Try this:
PStudioTask.NaughtyPath.Parent.MilfModeling.State = 0
Good luck.
Still trying to figure out how to fuck the preacher, got her do the bottomless pray but can't get past that.