I did some research and found varying numbers for sq footage costs, they ranged from 10-45$ a sq ft.

What are the requirements for 3 dwelling units in terms of lot square footage and FAR?

Depends on the square footage.

@Patrick RuffDeterming price per square footage for a rehab can be tough without actually walking through a property and knowing what type of rehabber you will be, for example can I get a floor done with materials anywhere from $4-$5 a sq. ft.?

The Torrance ADU development standard states "ADUs are not allowed in the Hillside Overlay or Local Coastal Overlay District unless the ADU is created from converting existing permitted square footage," which I assume are the areas you're talking about.

If people buy into the neighborhood are wanting square footage or number of bedrooms etc and don't care about upgrades, you have to take that into account.

If none exhort, look for “Efficiency” apartments that offer similar sq footage.

Even still, I was denied due to not meeting the square footage minimum with the lots.  

My mother is being my boots on the ground for this one, and she’s pretty confident in selling for 165-180k with this square footage and area.

What are the sq footage of these properties?