Hello everyone,I put an offer in on a duplex that needs a lot of work and will not pass conventional financing or standard FHA financing(the biggest reason being no heat source).

The front half of the building is a 2500sqft house and it needs about 20k to bring is up to standard. 

Standard 30yr mortgage.I never even knew to deduct depreciation until ~2014 when I finally began to expand into more real investment oops (have a total of 4 rentals now).

They can not only cost you an arm and a leg if you follow their standard pay off schedules, but they can seriously undermine your loan approval chances with a lender.If your debt is tied to a fixed mortgage, I wouldn't worry about it as much as long as your overall DTI is low & payments are easily made.

Just wondering how much time they should spend - I imagine some materials such as insulation are fairly standard whereas other things like countertops might require more homework in terms of selection and taste.

Honestly, driving for dollars can find distressed homes that are not on the standard lists.

It has good rent to value ratios for San Diego (which means less bad than most locations in San Diego - not good by other location standards). 

To piggyback off of what everyone else is saying, the VA has some strict standards for qualifying a property.

To do % of two numbers, I always cheat and go to this calculator: https://www.marshu.com/articles/calculate-percent-with-simple-number-percentage-calculator.phpEstimate: when pulling a list from a data source (like listsource.com) - the site estimates the equity by how long the mortgage has been in place and estimates payoff based on a standard amortization rate. 

Each will have their own standard, and it may be that you've spoken to one that only like high end rentals.