I'm not so sure its up to the realtor to decide who can and cannot afford to buy a house. That's for the bank or mortgage lender to make the call.
You're correct. The Agent DOES NOT make a final decision on who's qualified for a loan.
But his or her knowledge and experience does serve as a real barometer regarding what the odds are that anyone will pass muster with a Lending Institution. And it is incumbent upon us to stay abreast of current mortgage rates, loan programs and the qualification procedures being employed at any point in time.
We always recommend that Buyers gets "Pre-Qualified" (at a minimum) or preferably get Pre-Approved BEFORE commencing their search or consuming any Agents time and resources. It saves time for everyone.
Experience reveals that many Buyers refuse to take that advice, insisting instead to postpone that visit to a Lender until AFTER they have located the property that they would like to purchase. And, of course, they always think they know best. In reality, no one enjoys visiting a Lender and revealing their financial capacity and/or weaknesses.
A lot of time can be saved, and if that step is performed at the beginning of the search process . . . . but every Agent has experienced the Buyers who say they have certain resources, or think that some relatives will help them make up for their own deficiencies. Believe it or not, some Buyers will actually tell fibs about they purchasing power !
In the end, the Agent is the only Guardian of his time and resources . . . . he's an Independent Contractor. He has to make sure he's spending his limited time in the right places. As long as he's not discriminating among protected classes, he can choose to work with whoever he pleases. He has to be jealous of that time.
Some people have personalities that clash. Some people refuse to take direction. Some people are perpetually late for appointments; some people lie. Some people have a lot of income; but it's strictly cash and they have never filed a 1040. For us, income that isn't documented is the same as no income.
Even when people aren't entirely forthcoming with information about their financial resources, they will often still reveal clues that give us notice of what the likelihood is that they will ever get to a Closing Table. It's our job to listen for these clues. (On the other side of the coin, the same sensitivity to picking up clues holds true with our Sellers)
I always like to know "who" I'm working with early. Someone else might wait until the end.
That's our decision.