I have a friend who lends or gives us money to help us out.
Am I allowed to give him mishloach manos on Purim – or would this be considered some kind of ribis?
Would it be better to give it from our family to their family?
The main issue is the concern of interest (on a rabbinic level) for a current or recent loan.
If you give the friend mishloach manos every year on Purim (including a period of time before he lent you money), and you give him the same sort of mishloach manos this year as you give him every year, it is permitted. If you do not give him every year, or if you usually give him a small mishloach manos and this year you wish to give him a large one, it is forbidden.
In addition, you may not have intention of giving the mishloach manos in return for the loan.
Sources: See Yoreh De’ah 260:10, and commentaries. The above applies for a time in which money is actually owed to the friend. If money is not currently owed to the friend, giving a larger-than-usual mishloach would be permitted only if this would not be associated with the loan, meaning that a considerable time has passed.