I run a dealership. We have a lender choice forms and ask the customer to select several lenders or all the lenders. Save a copy of the form and the loan decision on each in case of a future audit to prove you gave them multiple choices of lenders who competed to give them the best rates and terms.
You are not to discuss exact payments, rates, etc., unless you are a licensed mortgage originator. You may deal in generalizations however, like payment ranges or guide them with rules like, "you can calculate an approximate payment by using $10 per thousand"(or $12), this will get them in the ballpark, or a $40K home will be $375-$450ish.
It's kind of nice not being the bad guy in many instances of delivering the news of needing more money down, shorter terms, etc., just let the banker be the bad guy.