The marriage is legitimate according to Islamic law as you are actually intending to get married (that is, it is not sham or a joke). Certainly, both women and men marry for money, social status, or other perceived advantages all the time.
Ethically: Be sure to treat others as you would want them to treat you. Act in a way whereby you will feel secure standing before Allah in the next world and will have a clear conscience. Avoid other sins, such as lying, deception, or neglecting the financial, spousal, emotional, or other rights of either spouse. This may be difficult if you are trying to go to another country.
It is generally considered unmanly to leech off of a woman, and certainly from an Islamic perspective, it is your obligation to look after her financially, rather than vice versa.
At the same time, life is not ideal, and many people right now are dealing with joblessness and feel desperate, especially in some regions or situations, or have political or other problems. So it is understandable that everyone has their own situation that they are trying to resolve.
Islamically, she is under no obligation to share her wealth with you or your existing family. Women often have good intuition, and unless she feels there is genuine affection and commitment, she might not be forthcoming with her money.
Also keep in mind that second wife situations can be messy. Sometimes a person may think they are marrying someone just for practical reasons and then end up falling in love. Or, one of the women may initially think she is ok with it but not be able to tolerate it. There can also be complications with how children handle it. This is just advice and not related to your main question.
You could also consider what is narrated from the Prophet (S): "He who marries a woman solely for her beauty will not find anything he likes in her, he who marries her for her wealth will be deprived of it as soon as he marries her, so look to marry women of faith."
