What to look for when buying a property in Europe?

Hello, I am thinking about buying a property in Europe, to use it as a long term Investement and maybe a place that I can relocate to if I decided to immigrate after many years. What is the best places to buy an apartment property in now? In terms of price and quality and location, also do you recommend any agencies to deal with? I've looked in Spain and Sweden, also in France and Portugal and Luxembourg, I don't have much experience in the best location, I don't mind as long it's a city and safe, I am keeping it open because my budget is limited. Any help would be much appreciated