When contracts are skewed to one side contrary to local customs your lock on the property may be very weak.I've sent standard contracts to sellers to sign and send back, done as an offer from the seller as it's unsigned.

At my institution we do 20 years as the standard.  

Ended up being a home run - Fannie Mae had already put it to rental standards with new paint and carpeting.

Standard homeowners forms have reductions in coverage when a house is vacant or unoccupied for a set period of time (30 days, 60 days, etc.). 

You should use whatever the standard is for your area and type of property.  

I am approved for the 1 Million dollar credit line, but with only 150k disposable, I won't be able to use it to its full potential leaving me in a position where I may not benefit much from it.I am the type of person that hold myself to a high standard, which is above average.

The few that do will not provide as high of a LTV and the interest rates are a lot higher than a standard HELOC.

While it is not standard to do this it does happen.  

The one I kept because I found it the most valuable was "Wealth Protection Secrets of a Millionaire Real Estate Investor" by William Bronchick.If you've already got your real estate agent picked out I would recommend asking him/her to walk you through your state's standard residential purchase contract.  

This is typically correct for standard residential mortgages.