Basically something that needs no more than $30,000 in rehab, mostly cosmetic upgrades.

Hey @Carl GraffI'm certainly no insurance-wiz, but my understanding is similair to yours in that most will use cost to rebuild as the basis for your premium.My guess as to why you're having trouble finding info online is that I think it's nearly impossible to give a blanket assumption to be used on a $/sqft basis nationally, and even locally I think you'll find challenges (the only difference location makes in the cost-based evaluation is the price of labor, for the most part, and does not address the issue of failing to account for different quality finishings/condition/upgrades). 

The final contract sales price was $145K with 3k seller assistance.Lessons Learned:1) Always upgrade a half bath to a second bath when space permits.

How could I analyze the amount I can afford to spend on an upgrade based on projected gross rent receipts?

The age of the house not only means that you will have many many issues, it also means that touching anything will likely trigger code upgrades.  

@Long VangARV is generally looking at comps that are similar to your expected post rehab condition, depending on what you're upgrading and the quality of the upgrades (granite vs Formica as an example).

This way the rehab will be spread out for a year and you will have upgraded property.

Remember a broken clock is still right 2 times a day.  

Kind of related, should I install conduit to the attic for future upgrades?

Basically he was buying new during opening phases (best pricing), building bare bones, doing his own upgrades after closing and selling.