How do you evaluate trades in a contract league? There are so many variables that I’m not sure how to go about it yet. What do you do to figure out if a deal makes sense?
		
		
	 
Lot of variables for sure.  Here are the 3 main things I would look at:
-Are you competing NOW?  If so, I don't look as hard at years left and cost of contract, assuming I can fit both in.  For instance, I traded for Kyler this year even though he only has 2 years left on his contract because I needed someone to pair up with Richardson and since it's a 16 teamer, QBs are harder to trade for and I am in position to win now.  If I was a rebuilding team, not a deal I would make.
-What is your balance of young and older players?   Great to make a "win now" deal, but if you are dealing for an older player and your overall team is older, I would think twice.  I added Mike Evans in Free Agency this year and paid him almost half my cap, but it was OK since I have a lot of younger, cheaper WRS and had the space.  Only a 1 year deal and will reevaluate next year.  I also traded Diggs for Shakier and Jaylen Wright because after I signed Evans, Diggs was my #5 WR and wouldn't start most weeks anyway.  Shakier will do fine during bye weeks and I got younger and cheaper at two positions.
-I like to trade for future picks rather than have a bunch of depth early in the season and will risk that my players will stay healthy.  If I do get a lot of injuries, I can take those picks and trade them to teams that are out of it midseason.   Had to do that last year when I got hit hard with injuries.   You get more value in-season than off season.  Also try to pinpoint teams that think they have a better team than they do.  For example, I traded Ridley right before the season last year when the hype was high for a #1 pick from a team that thought he was a playoff team so figured the pick would be 11-12 range at best.  I thought his team was more a .500 squad and potential for disaster with an injury or 2.  That happened and the pick ended up #3 overall. 
There are a lot of different rules for contract leagues so this may not be very helpful depending on yours