We got a quote from a highly qualified mobile home repairman for $3100 for skirting and stairs, and he planned to build a fence around the perimeter then install the skirting to it.

Instead, there is a tile perimeter all around the unit (seriously, every single edge, about 9" high) so it essentially created a giant swimming pool.  

One inside the perimeter and one just outside, both in the south.

Some tips before you start pulling drywall:Check all around the perimeter of your basement. 

My question is should I buy a foruplex/Single family homes inside the perimeter or should I buy a lot and build 4-5 studios and rent out (Inside the perimeter)/ What are your thouhts?

Bright lights on motion sensor.I would also second adding some pretty, but thorny, plants along the perimeter such as the Holly or Roses.Perhaps bars on the 1st floor windows?

Just get reading from various perimeter walls. 

Hello all,  I need to complete the fence around the perimeter of my Denver duplex and I would like to solicit a few bids to see what it might run me.  

I think if you are reselling or renting you can power wash the white, then trim out the perimeter with a nice contrast or light pastel - whatever color you should first determine the purpose.If you are owner occupant it is an esthetic change also consider what is the most cost effective.Much Luck!

Maybe water the perimeter of the foundation for a couple hours to see what happens.If something major is found then check that against the Seller's Disclosure.