My thought was that if serious damage was uncovered in the inspection period then I could back out.

Can anyone share their thoughts? 

Your thoughts/advice is very much appreciated!

I've never thought about buying directly from them.

This would be my first investment and I have no experience, so I know it would be a massive stretch.Any thoughts?

What are your thoughts considering I could increase rents and wait for rates to drop and when that happens refinance again and realize much bigger profits

As far as direct mail is concern,  you'll need to be prepared to be consistent and have a good budget for mailers. 

My thought is since I would find a single family home into a duplex that has had a very short, or possibly no rental history it could cause trouble at appraisal since NOI would be difficult show.

Honestly, it's not as big of a deal as people make it out to be as long as you're addressing mechanicals, or you're prepared to.

Based on the train of thought you shared you are completely ignoring a critical piece of the equation which is your own capabilties and whether you have the ability to execute on the opportunity.