New Construction vs. Existing Building

This is actually a question about commercial real estate, but I don't know where to post it other than here.
I have been looking to purchase a small (2000-4000 sq. ft.) commercial building for a business than has outgrown my home office. I have been looking in a depressed neighborhood of Los Angeles County at buildings in good shape as well as fixers. Today, the idea of buying a vacant lot and building on it popped into my mind. All I need is 3000 sq ft. of open unfinished warehouse space, with 1000 sq. ft. divided into three offices. Not even fancy offices. Is there a rule of thumb for comparing the price of new construction with an existing building?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.