I don’t think that Felix, when he calculated 4%+ return, considered the property management fees or the time and hassle that it’ll take him to manage his property. He said that he doesn’t live in San Diego. A few plane tickets and trips to San Diego will kill his ROI and turn it negative very quickly.
Stocks, bonds, CDs, and most financial intruments are marked to market instantly. With houses you have an illusion of wealth and stability. But it’s only an illusion.