Growth in lending for property investors may grind to a virtual halt, if the modelling by one sell-side analyst proves on the money."The major banks' investment property loan growth [will] drop to around one per cent" in 2018, Richard Wiles and his associates at Morgan Stanley Australia projected in a research note this week.APRA's new cap on interest-only loans, restrictions on higher-risk lending, more differentiated re-pricing and the prospect of further measures to prevent the build-up of household debt and address housing affordability concerns "sees our forecast for total Australian housing loan growth slowing to around 4.5 per cent," Wiles said, "with CBA the most and ANZ the least affected."Wiles weighed the macroprudential measures of APRA as a hazard more on the business lending side of bank asset quality."We think credit rationing increases the probability of a weaker economy and higher non-housing loss rates next year," he said.The restriction on interest-only loans "means that the value of principal and interest loan approvals need to increase by around 15 per cent to maintain the major banks' approvals at 2015-16 levels." he estimated.This may happen, putting a dampener on credit rationing.Wiles wrote that "our initial assessment is that a switch to P+I and tighter serviceability criteria will not prevent the average borrower getting a new loan."