What is Garantia, guaranting? Rent for 2 years and perhaps (another 4 years rent + court fees) more till they are able to get you out for not paying the rent..
That would be my calculation.
Not the rent of one versus rent of the other. Rather the sale value of the small one is equally to how many years of rent on the big one. Plain and simple.
The other thing..its not that their are 100's of options for a high end apartment owner in his choice of possible tenants. The higher the rental..the tougher to rent it out.
==
The other thing is that even without garantia, so many landlords are ready to rent you a apartment if you pay rent for 12 months or 24 months in advance. If it was all about security for the landlord , what is the guarantee, I will peacefully vacate after 2 years despite paying 24 months rent in advance?
In my opinion, the garantia is just a stupid/ superficial guarantee for the landlord for recovering any unpaid rent and any court fees and waiting time to hoist you out eventually.
==
Their is a difference between a 'house squatter' who forcefully takes over a uninhabitated house versus a tenant who has done proper paper work and has pledged to pay rent. A house squatter will never pay rent and will not leave ever. A tenant has signed in front of a notary to pay rent and then suddenly he/she stops paying rent for some "sad" personal life hassles. So the owner needs to be guaranteed that till the time, the court gives a order to evict this tenant, at least the 'garantia' will help recover the unpaid rent/waiting time for eviction.
==
A tenant who has not paid rent can not just sell of the house and disappear in thin air! Its only about unpaid rent..so for 2 years of rent + 4 years of waiting time + legal fees. That would be my calculation in buying a cheaper small apartment to be be used as garantia.