It's simply not fair to the seller for you to tie up the property for a month with no compensation if you back out last minute.The amount of money considered "fair" for earnest money depends on the area, the market, and the seller. 

Then, you remove all of the damaged materials, and depending on what happened underneath, if nothing, then you're done.

It depends on your plan.

It all depends on the investor.

Of course it depends on your market and your area but thankfully there area deals to be had here in Chicago and in NWI. 

depends on the size and condition.

The questions you should be asking (and the answers to the one's you've already asked) will largely depend on you and what it is you are looking for.

It will also depend on your investment situation.

Sometimes I'll take a skinnier deal than at other times depending on the opportunities available.  

I have a side job, so will not need to depend on selling as many homes as possible to survive and I live minimally.