To break into Michael’s house walk up to the gate and climb over it. Enter sneak mode and take out the gardener. Walk to the right side of the house to the parked truck. Jump onto the truck:

Climb onto Michael’s truck.

Climb onto the roof and go through the open window to the right. Enter sneak mode again and go down the stairs. Turn left at the bottom of the stairs and left again shortly after to go into the garage:

Turn left and go into Michael’s garage

Now you can enter the car.