Should i expect 30% expenses on top or mortgage?

[Fabien Chanoz]

Hello to you all i was wondering that most people fail in real estate because the mortgage and the expenses end up being more than they expected and then they find themselves under 

I was wondering how should i calculate becore buyng not to be taking from my own pocket? I heard about the 50 percent rule but it does not seem realistic or maybe i did not undrstand it well Should i expect 30% expenses on top or mortgage?

IN Paris where i live found a plce 90 000 EUROS 10 M2

RENTS FOR 450  Even if the mortgage is 350 Euros it is not  agood deal right?

THANK YOU