A guaranteed zero ROI is better than a negative ROI which you can get with buying a house (e.g. the house you can resell it drops due to the market and you can't afford the mortgage for some reason...)
But I should have said renting is a sunk cost. There is no investment component at all in renting.
I would say low cost index funds are a much lower risk investment than a mortgage. They also have the advantage of being very liquid in the case of actually needing your money. Rent is not a sunk cost, this is a common misconception.
There are many good reasons to buy a home, but do not think of it as an "investment". Compared to other investment options, it's a pretty terrible one.
I highly recommend reading this article to learn more - http://jlcollinsnh.com/2013/05/29/why-your-house-is-a-terrib...
The question is how do you invest the extra leftover money: in home equity tied to the property with running costs, or in other investments (stocks, bonds, your own business)?
If rent < mortgage interest + other housing sunk costs and you invest the delta, renting can have a substantially higher ROI than buying.
Additionally, even if the house is paid off, you're still on the hook for all repairs, maintenance, etc. And if your neighborhood starts to go down the tubes, your house value can quickly decline as well.
I think property taxes in US already vary a lot from state to state. It certainly vary also from country to country. It's something you need to be aware to take a decision on whether it's a good investment or not.
Ultimately, all these costs are also embedded into renting price.
Also, recently, I've been looking at housing market in Munich and it's very very expensive. Renting is ~20% more expensive than in Brussels and acquisition is +100% more expensive. So, although I admit I do not know rest of Germany housing market, I have some troubles thinking why Munich would be more expensive than Brussels. And I certainly miss, from that perspective, why German system would be more interesting.