In Sapain:

people's age: men, indifferent; women, inappropriate.

People's religion: indifferent.

people's family: appropriate.

people's house or car cost: appropriate.

people's salary: entirely inappropriate.

All the best!

In Germany I wouldn't ask for the salary or the price of a house but it's no problem to ask for the price of a car.

People are not used to be asked for their religion, but I think most people wouldn' mind.

Some people do not like to be asked their age, so I wouldn't ask everybody.

To ask for the family shouldn't be a problem. Most people are happy to tell you everything especially about their children or grandchildren.

It always depends on who is asking, and why.

I'm from the US.   It is important to remember that people's feelings vary on these questions.  I have tried to provide general guidelines for you. 

people's age - It is okay to ask men, and children.  Women tend to be a little more sensitive about their age so it is best to refrain from asking this question. (As I mentioned, people vary.  I have no problem sharing my age with anyone who asks.  I also know several women who aren't bothered by this question.)

People's religion - No.  Religion is very personal for a lot of people.  Some people are very open, others are not.  If a person doesn't want to discuss this they will normally say so; however, you risk awkwardness in future communication.  (Again, people vary so it's best to err on the side of caution, or approach this topic delicately.  It can be a hot-button issue for many.)

people's family - Yes. 

people's house or car cost - No.  It is inappropriate to ask how much a person paid for something.   If you want to find out, it is best to say something like, "Was it expensive?" or "Did you get a good deal?"  At that point, the person can decide if he or she would like to elaborate.

people's salary - No.  Unless you are speaking to a child or family member, this question is always inappropriate.

I hope this helps.

For reference, I am from the United States.

Age: It is ok to ask for a person's age if the person appears to be young. If the person appears to be over thirty, you should not ask them for their age. If you must ask, it is more socially acceptable to ask men for their ages. Never ask a grown woman. Don't do it. She will murder you. If she wants you to know, she will tell you.

Religion: It is generally acceptable to ask about a person’s religion if you know them on a personal level. You should not ask about a person's religion if they are a co-worker or if you just met them.

Family: It is socially acceptable to ask about a person's family. Conversations involving family are generally considered small talk (polite conversations about uncontroversial matters). However, when you are first meeting someone, it is impolite to ask about deep family issues. For example, it is considered fine to ask an acquaintance about which college their sibling attends because it is not an emotionally charged issue. It is not socially acceptable to ask an acquaintance if any of their siblings are suffering from addition issues since this may cause a lot of emotional pain.

I live in Saudi Arabia, but I am Palestinian. Every time I go to Palestine, my relatives and even complete strangers do not hesistate to ask me about how much I get paid or how much we pay for rent. That makes me feel very uncomfortable, but this is the impact of the social closeness that Arabs have in general. It's also quite normal to ask about one's family, religion, or age, although asking about a woman's age might make her a little uncomfortable, especially if she's an older woman. I have noticed that Saudis are better are maintaining an appropriate reserve in respect of others, although I have been asked here several times about how much I get paid.