Residency in Bulgaria

As you know all European Citizen can take up abode in any of the other member states with the same right and privileges as "locals" It also means that your pension payments are also not affected by any penalties.
Good luck

EU nationals
If you are an EU national , you do not need to show your national ID card or passport when you are travelling from one passport-free Schengen EU country to another.

The passport-free Schengen area includes:
Austria

Hungary

Norway

Belgium

Iceland

Poland

Czech Republic

Italy

Portugal

Denmark

Latvia

Slovakia

Estonia

Liechtenstein

Slovenia

Finland

Lithuania

Spain

France

Luxembourg

Sweden

Germany

Malta

Switzerland.

Greece

Netherlands

You must still show a valid ID card or passport when travelling to or from Bulgaria, Cyprus, Ireland, Romania and the United Kingdom. Though part of the EU, these countries do not belong to the passport-free Schengen area.

"Passport-free" refers to border checks only – it is still always best to take a passport or ID card with you, so you can prove your identity if needed (if stopped by police, boarding a plane, etc.).
Driving licences, post, bank or tax cards are not accepted as valid travel documents or proof of identity.

Sample story

Lars is Swedish and holidaying in Spain. He took his bank card with him – in Sweden, it's accepted as proof of identity.

But Lars could get into trouble if the Spanish authorities want to check his identity, because the only valid ID documents they recognise are national ID cards and passports issued by the Swedish authorities.

What is a valid ID card/passport in your country?

Entry refusal
In very rare cases, an EU country can refuse entry to you or your family members for reasons of "public policy, public security or public health".

This means the authorities must prove you or your family members pose a "genuine, present and sufficiently serious threat".

You are entitled to receive this decision in writing, stating all the grounds, and specifying how you can appeal and by when.

http://europa.eu/youreurope/citizens/tr … dex_en.htm

My fiance is Bulgarian, and she resides in France - She Doesn't use a passport - only I.D. Card.