One of my mates has 4 properties, another has ten. Both are mums and dad investors and both have about 90% of the value borrowed.
Most other investors I know have one. In fewer cases 2. Doesn't really matter, how many they have, given a correction, enough will pull the plug to do some damage to the market prices.
The guys with 4 and 10 say an extra 1% in rates would wipe them out. If they say this, it will probably happen, either by local or international machinations. Neither show any inclination to sell any, in fAct the guy with 10 is buying more. Admittedly he has chosen some very high yielding properties, but he still says an extra 1% will result in him selling most of these. He simply believes that rates can not go that high anymore.
