Here’s my advice for what I think may help a woman, when learning if your investment in a man is worth it. I'll make this short and sweet.
You must learn as much about him, mainly his childhood as possible! Knowing how he was raised, what he went through and things of that nature can help you spot clues to his current characteristics.
Ask a lot of questions. You’ll start to see patterns with his emotional reactions to certain situations, that may either be warning signs (a.k.a red flags) or green lights. You’ll notice the different interactions he’s had with particular females and how he’s treated them whether they are family, friends or associates. Women are naturally born private investigators, so I figured starting from there would be your best bet. This is just me speaking from a man's point of view from being around my friends, who have the tendency to use women for personal gains.
I hope this may help anyone who’s struggling with this.