No Loan Rep can know the interest rate a lender will charge your client until after they have submitted their application for a loan. Interest rates for 30-ear fixed rates will vary according to your clients credit score, amount of deposit down, type of property, and other qualifying ratios that lenders hold in my opinion, (secret).
Loan Reps won't know until they have gotten all of the buyers financial paperwork in front of them In addition, mortgage rates can change daily. No Loan Rep can confirm the rate you will pay until the day you lock, or the day financing occurs. If you ever get offered a low ball rate quote, be prepared for the old "Bait and Switch"