Address for Residency

It looks like I have sold my house but I want to retain Hungarian residency. At the moment I am trying to find out about the various options for doing this. I will be living just over the border in Croatia and will probably do shopping trips to Hungary about once a month. One option might be to buy a cheap, ruinous house for about a million ft but I'm hoping I can find an easier way. I see you can rent a room in a village house for about 18,000ft per month, so that might be a possibility. I have wondered about a box at a post office (if such things exist) but That might not be valid for residency. Do I just have to notify change of address or do I have to re-apply for residency and show proof of income?

If I do need to buy a house I am likely to end up with a garden to maintain. I don't know about utilities. Would I be obliged to have electricity for a property to be deemed habitable? I notice that a lot of vine houses don't have electricity but perhaps they also don't have postal addresses?

A "winehouse" that does not already have residency rights must have water, electricity and waste disposal (sewage or on site treatment) to acquire a new residency permit. It is not easy.

But....

If you are in Croatia for more than 3 months you have to inform the local Croatian government of your "residency" in Croatia. Just having a room or building in Hungary will not legally maintain your residency. Residency is where you live and spend most of your time, not where you just have property. So you really will have to travel back and forth and probably stay a while in Hungary to retain Hungarian residency (I do not think just coming to do shopping will suffice).

Seems like quite a bother, and fraught with problems and possible legal issues. And if it is determined at some point by Croatian authorities you actually are living in Croatia illegally, you could loose Hungarian residency anyway and then become ineligible for Croatian residency. Seems like quite a risk to be taking. Why not just file the paperwork for Croatian residency?