We live in a litigious society where there seems to be a need for someone to take the rap if ever something goes wrong. However not everything that goes wrong can be laid at the door of professional advisors and this seems to be one of those cases. Yes, advisers should be held accountable for the advice they give, but advisers can only be held responsible for something which they have a contractual or other duty in law.
The advice that is requested should be within the area of expertise of the particular adviser or they should not advise upon it. In this case, the client is blaming the adviser because the property could not be let out. It may be that the property is unsuitable for letting or it may be that the local authority will not give planning consent for its use as flats. We do not know the reasons which could be far removed from the area of expertise of the introducer.
There is arguably a connection between affordability and general advice to a customer for whom you are arranging a buy-to-let mortgage. I would think it is stretching any duty of care for the adviser to be forced to warn the customer that rents may not be obtainable other than general advice on affordability of mortgage repayments. The job of the advisor is to arrange a mortgage suitable for the purpose of the customer.
This customer will be deemed to have enough intelligence to understand that rent needs to be received to make the deal a sensible or affordable one ‘ it seems to me that unless the introducer has gone outside the normal sphere of advice then this particular borrower is clutching at straws.