Only one offer I've had that wasn't accepted and that was fine, I know it was fair and I walked. 

Meet them in person if possible when you walk through.

It's more likely an experienced investor won't walk when something comes up. 

Sometimes a little walking around money at the end of hard days work is a nice reward (even if you pay a little tax on it)

I do have a general contractor walking through with me soon to plan out rehab and costs, but I think working with a property manager will be the real cherry on top.

The job would be easier than a home inspection because they aren't testing all the outlets and appliances, walking the roof, crawling the attic, etc.

They still have to present you with a written agreement to review and sign, so you still could walk away. 

Unfortunately, most Sellers don't have a clue, they structure deals that are far more favorable to the Buyer, and they lose money when the potential Buyer walks away (over 80% of the time).If you're a seller, forget it and move on.

Ps.I have a move-in move-out check list and plan to walk the property with them on the last day to verify the conditions before returning the security deposit. 

When it doesn't, and the Seller gets a high appraisal, I walk away.