U.S. Retiree Moving to Croatia - residency length and length of stay

We are two retired couples moving from New Orleans area to Istrian Penninsula, probably Pula. 

We ar currently visiting looking for apartments but also checked with police station on long term residency requirements. 

We learned that when we come back for our permanent stay we will need to submit our application to the local police department with translated proof of health insurance, means to support ourselves, place to stay (I.e. rental), passport, birth certificate, picture, reason for application. 

The police office told us that after one year you must leave for at least 6 months before coming back and reapplying.  This was surprising to us as we intend on staying for multiple years and had not previously heard of this requirement.  Does anyone have any experience or knowledge of this requirement?

Thanks
Mike

would be good to know about this ... anyone know any more details .. thinking of more permenant move too and also retirees are part of our group move so would like to know if this is the case.. they dont really want to keep going backwards and forwards???

I hadn't heard you couldn't renew the Residency permit, actually I had heard very easy to renew but with Croatia now fully in EU there may have been changes. Most Americans I know ( suprizingly not a lot) look at buying a small place and under that visa after 5 years of renewing can become permanent.

Owning a property any property makes it easier for residency permit, as does owning owner of Croatian company- problem is owning a Croatian company very expensive to administer.

As an aside Pula area if one of my favorite places for a tranquil life except sometimes during high tourist season.