If you can reasonably throw up a new wall and closet, turning a 3 bed into a 4 bed, that is a great place to start, but only if it works for the property and you have at least 2 full bathrooms.  

The blood spatter on the walls and floor?

Add a couple of chargers, no problem. 

It's understandable that unexpected things arise sometimes, especially when you're opening up walls or dealing with older electric or plumbing.

My friend said his client nearly bailed when she found unexpected wiring issues behind the kitchen walls..apparantly the seller hadn’t touched that electrical since the Reagan era..but with a patient electrician who understood the local code and a carpenter who improvised a shelving trick in the diningrom, they ended up selling above asking.Flipping and building can get tricky, especially once you start thinking bigger.

For example if you asked him to only paint a wall but the wall does not look good because the drywall itself is bad - that is not his problem because you did not want the drywall fixed.Specify what it is you want done and if complete you will release the payment. if he disagrees then he may sue and then let the court decide. 

Like someone else mentioned, doing a short term rental in a secluded basement that is very private and walled off is one thing, but sharing the same refrigerator, kitchen thermostat, etc. with a complete stranger seems like it will introduce more problems than what the money is actually worth.

When we removed some of the wall we found that there was damage to the wood.

The worst thing here is people who he recently took money from - yes some people are still being conned out of their money - lost it all to the court.I can see him working on 4 houses at the moment, and each ia having work performed out of sequence with 3 of the 4 still having no front entrance door installed, but they have still finished the internal walls and laid the flooring.  

You will also need wall hangings and art, not to mention kitchen stuff like silverware, pots and pans,