Be able to give ball park estimates like tax value per $10,000 and cost to insurance.Then up that to a duplex or quad plex. 

We low balled & got a 3-unit next to one & the tenants always complained about paint fumes & noise.

I do know just getting in and investing into something we take the time to evaluate and crunch numbers would be a smart move and just get the ball rolling. 

Also, don't be married to that home value, an assessor will come in and low ball it everytime and possible say it's worth 85k and then you get 75-80% of that.

I think 6' is the standard, though my guess is inspectors probably eye ball it differently.We used George Gavin for our rental inspection.

@Christopher Ball thanks brother!

If you had a crystal ball and think you can time the market, you wouldn't be asking for advice here. 

I was told that it might be best to get some idea of what investors would pay for it, so that I can make an agreement with my grandmother to buy it at that price (so there is no chances of family members saying I low balled her). 

How much on a 1700 sq foot single home full rehab Estimated around the ball park ?

I understand wholesaling foreclosed homes is a whole other ball game.