referal fee etiquette

[Mike Landry]

Is it ok for an agent to ask for a referral fee if they refer a client to another agent that buys a house?  What is industry "standard" if one exists.  $500, .5%?  Is it best to keep referrals inside the same brokerage?  Is it appropriate to ask for a referral fee or should it only be taken when offered first?  Is there certain paperwork/disclosures that need to be filled out?  in Texas fyi.

Thanks!