The Ultimate Meaning of Having a lot of Money
[Having a lot of money is considered as the ultimate goal for most of us.]
"Having a lot of money is considered the ultimate goal for most of us."
** the 'as' after 'considered' is not necessary
[Nothing is wrong with that unless possessing that money will not make us forget that the ultimate meaning of possessing it is helping others as much as we can do]
"Nothing is wrong with that unless possessing money makes us forget that the ultimate meaning of it is to help others as much as possible."
**I think this is what you're trying to say here, your original sentence is what we would consider a 'run-on sentence.' Since you're not referring to a specific kind of money, putting 'that' before 'money' is not necessary.
[Otherwise we don't deserve owning it. ]
"Otherwise, we don't deserve to own it."
**You're so close! The infinitive form of 'own' is most appropriate here.
[I will go further to say that helping others should be the main motivation to have that money.]
** Taking out the 'that' before 'money' would be the only correction in this sentence.
Let me know if you have any questions (: