Rental Unit has a leak

[Clayton Carr]

I’m pretty new to being a landlord. We bought our house a little over a year ago and at first everything was fine. Winter came and since then the rental unit has flooded every time it’s rained. We’ve checked our gutters we’ve extended their drains and directed the flow away from the house. We’ve put silicone sealant along the walls of the portion of the house that is affected all the way to the foundation. There’s no indication that the leak is coming from the roof so it’s got to be from the walls or the ground but I’m at a loss on how to diagnose the cause and fix the problem.