1) Can you use the lender multiple times after building it? This is assuming you pay it off and then use it again OR do you use lender only right after you build it (which means only once per game).
Yes, as many times as you like (once per turn of course), as long as you don't have it at the start of your turn when you want to use it (so you've either paid it off or your opponent has taken it in a prior turn).
2) What happens when you use lender for village or camp? Do you get to use the extra meeples permanently throughout the game or do you just get to collect a resource. If you collect resource, do you move the village/camp meeple prior to resource collection?
Only that turn, and yes you would have to move the meeple before collecting the resource it's on - same as any regular meeple you have access to: You have to move them to get the resources they land on; you don't get resources from meeple you don't move.