Rip wasn't very bright.....
He wanted his 50k back but:
Brushed off Clay when Clay told him at the hot tub that he'll sell his car or do "whatever it takes" to get him the money. Rip tells Clay "it has nothing to do with you', well, if i'm trying to get my 50k back and this person has the means to get the money...well, if i'm Rip, it has EVERYTHING to do with you".
Near the end, when Julian comes to Palm Springs to tell Rip he's quitting working for him and sobering up. If Rip had a brain he'd realize that as long as Julian was drugged out he'd never get his money back. Again, Rip needed to let Julian stay off drugs and get back to having a relationship with his dad which in turn gives Rip the best chance of getting his money back. Rip should have let Julian go back to LA and try to straighten his life out which probably would have resulted in him getting his money back.
I know Rip said to Julian "we've heard this *beep* before", but at that time he wasn't owed 50k...things change.