First, this is one of my favorite strategies.  1 - How did you arrive at the rehab cost?

It is trending "rough" for a neighborhood. with lots of new arrivals to the country from places that don't speak english.

I offered to help remove trash recycles compresser cardboard remove left over items from refrigerator and pantry.She never returned so I hired a friend w truck to take to town dump.I drive a suburu and didn't have space to haul garbage.I had to repair split on inside of front door punch hole in hallway that was taped over.1 cat turned into4 so I had to wipe white silkey hair out of floor ventsalso vacume litter clean out garage refrigrater wipe and remove leftover stuff in drawers.Me rental had to set off 5 bugs bombs before she could sleep in home.I was quoted$800 for assurant pest controll to travel to sheltercove.I live in a rural area by the coast.I am ordering natural pest controll products and will hire a friend to spray.Northern calif doesn't have roaches so last tenants brought in.Last tenants are threatening me w lawyer if I don't return full deposit1800.I silent 15 hours doing repairs due to damage.I also had new tenants internet installer remove part from dish to mail to last tenants.Previous female tenant said they had that set up but new tenants have dogs in back yard.Also No one contacted me from previous renters about scheduling part removal.So as a courtesy I will mail back to Vegas and keep receipt.I am getting threatening texts demanding full deposit.Also they say I owe back rent from Sept 10 to Oct 1 but they didn't return to get what was left for me to deal with.I am cleaning vacation rentals and am still getting a list of damages.I'm ordering natural German cockroachkit online will arrive 2 days shipping cost 29 plus products gonna run another100.

New guy arrives, sees weird equipment, doesn’t know how to fix it.

Help me arrive at a value. 

Assuming for the sake of answering your question, if you paid $40k, you would want to invest no more than $30k to arrive at the market rental rate of $700/month.  

If this group of tenants moved in 5 years ago, compare the gallonage of water used  with what was used before they arrived. 

We can finance the build which we find is ideal for the bank doing the construction loan, they just take us out when the modules arrive onsite thus relieving their headache of how to secure their loan to a non-real estate module sitting in a factory somewhere.Feel free to message me and I can help you analyze this further.

If the auctioneer said SOLD before good funds arrived in the hands of the Trustee ... the third party deal is dead.Somebody sat on funds for a long weekend with an auction sale pending?

I've even removed CapEX (new property, minimal required), and property management, but still arriving at a negative CF.