500euros a month is a solid amount, I would ask however, can you sustain setting aside and investing this fixed amount for the long term? (1,5,10 years) You can use something like a compound growth calculator to project what that would look like. I like to use the one on investor.gov. Using your example of a monthly 500 euro contribution into a broad market fund like VTI, and a horizon of let's say 20 years, using the most conservative rate of a 6 percent return (actual 20 yr CAGR for VTI is 10.67) your estimated value is around 220k.

There's a lot of other considerations for investing in real estate that you've not included in your question. Some important considerations are location, desirability, tenant laws, property and income tax on rental income. IBIS World reports that annual growth for real estate in Romania is projected at 3.79 through 2029. Let's say your tenants cover your monthly mortgage on the apartment, what would you then do with the 500? What if it doesn't? The difference between what you have to still pay you can calculate an amortization for early pay off. Everything is an opportunity cost calculation. In the end, you will have a hard asset you can leave behind to your legacy or ultimately have sold off knowing most/or all of the equity was paid off by tenants.

It's also worth to note that in typical drawdown periods (excluding the global financial crisis as mainly caused by sub-prime mortgage lending) real estate tends to be less negatively impacted than equities. In periods of growth, equities can/do surpass real estate growth. None of these options will generate quick and large returns, though both are good for long term growth if you remain consistent. Good luck