Need some help here. I am helping a friend add an addition to his house. The new addition will be an in law apartment. The current service is 200 amp. The in law apartment will also be 200 amp. What amp size will the new meter can be?The new 200 amp panel is on the second floor.Can the disconnect for the new panel be located after the meter can?This is an underground feeder, does the feeder wires from the transformer need to be larger? Thanks Chris

CALL AN ELECTRICIAN!

You are obviously in over your head and do not know the details and codes needed to do a job like this.
Besides, you should NOT be "helping" someone do electrical work. Especially not on the scale of this job. The liability is way too high.
Do you have a license and insurance to do electrical work outside your own home??

More like call an "electrical contractor"!