I believe you can definitely serve God while being financially rich. God blessed Abraham, Solomon and David with great wealth. I believe the ones who are wealthy and love the Lord have riches, but money does not have them. They manage money, but money does not manage them. However, there are many whom God knows not to bless with financial riches because many will become secure in their finances rather then on God. It's one thing for the Lord to bless one financially, but we are not to over-work ourselves just to become rich. Otherwise, we are relying on the flesh to provide for ourselves rather then relying on God who is the One who provides. The question is, do they honor God first with their money or do they love money to fulfill their covetous desires? That is why Jesus questioned this rich man about lacking one thing and selling to the poor which is what he lacked all because his heart was towards his own riches and not in the right place.