What does one do when one finds out that one of your registered Brokers/Lenders is a proven scammer + Con Artist?

you should google them and also check the BRE website with there license number.

Don't do business with them?

If there is actually something they have done or sent you that is clearly violating specific laws, then I would first contact this individuals Boss/Manager to report this person, assuming they have one. If this is not the case or if doesn't work, then I would advise submitting a complaint to the CFPB. The "Consumer Financial Protection Bureau" was put in place by the government, to help protect consumers from these type of situations. Here is the link to do this: https://www.consumerfinance.gov/complaint/ I hope this helps!