Being in love should be paramount. Other, more practical, considerations involve whether or not they have a criminal record or any ties with their country of origin such as debt.
The first obvious consideration in the first place is that you are marrying someone who is already involved in illegal activity. That should be the stop sign.
One major consideration is possible deportation of your spouse, leaving you and any children born in the U. S. here, and your spouse in native country unable to return.
I would recommend asking him or she how many times has he crossed the border ilegally or legally, if he has had problems with the law for example dui etc.
