Is there a minimum notice period that I will need to give them ? 

Regardless, once you waive your due diligence period, you're out of luck.The only way you can get them to pay is to prove that they knowingly and willing misrepresented, aka fraud.  

I have completed 5 flips over a period 21 months and this will sixth project.

Remember to get them under contract first so you don't lose them, then do your due diligence while under the contingency period.

You can hammer you contractor or subs and that might work for a short period of time but to build a long term relationship usually all you need is light correction with the very rare kick in the a** that everyone needs every now and again.

You can play around with a typical amort. pay down in that time period and then plug in a higher interest rate to see what you could do to stay at the same cash flow.

Are you aware of any lenders with a short seasoning period ( no more than 6 months) that will refinance off of the appraised amount and will do a cash out refi? 

Contractors are licensed, period. 

Was wondering if there are any document in the "files" section on bigger pockets that others have found helpful in organizing & guiding you through the whole inspection period?

LOI is just a handshake agreement it's not legally bindingThen next have a feasibility period or more specific contingencies (financing, inspection, etc) to do the rest of your due diligence on the property to protect you as you move forward