The problem is you have to put in the effort to maintain/repair/rent out the property you have. If an effort is needed to maintain profits then I could as well

The problem is you have to put in the effort to maintain/repair/rent out the property you have. If an effort is needed to maintain profits then I could as well do many other things that bring better returns than properties. The idea of an index fund is that you don't have to do anything for it to bring relatively reliable profits.