Re: Concubines
The Quran, I feel, is quite clear on this. It does give permission for you to have a "right hand", however the context of this is still debated today. Secondly, within the Quran, you will find exhaustive commands to not spark a relationship with a woman against her will, and this goes for any sort of physical relationship. Including those of concubines. By my analysis, even taking a slave as a "sex slave" would be haraam if the said sex slave is being coerced into the relationship against her will, even if it is through an exploitation of a vulnerability (as there are verses also against exploiting vulnerable poeple and taking advantage of people).
By Quranic analysis alone, you should be able to come to a difinitive conclusion that you are not permitted to take a concubine, in the traditional sense of "I point to you, you are mine".
Moreover, you are highly encouraged in Islam to marry and legally take a believing woman as your wife and keep her, and as someone else said here, there should be no financial excuse not to keep a wife, as many women are financially independent and so finding a cost-effective way to enjoy a marriage is completely manageable, if you work hard enough at it. If I were you, I'd be trembling at the thought of taking a vulnerable woman as a "concubine", because in today's age that usually translates to keeping an illegal sex trafficking victim against her will in your home, and do you really need to post a topic to find out if that is halaal? If there were other scenarios in your mind, please do share. Perhaps I've misinterpreted you, but the term "concubine" in today's age really just means having a sex slave hidden in your home.
Finally, your religion does ask you to follow the law of your land. Therefore, if you are living in a country, where keeping a sex slave is outlawed, then please do not even consider it and try to respect the laws of the country you inhabit. MOST countries do have anti-sex trafficking laws even if they're not necessarily strictly adhered to at border patrol points.