I know the formula is a guide/base line but when you have ARVs hovering around the million dollar range, is there a rule of thumb or a percentage amount increase to determine purchase price?

Let them guide you.

As a realtor doing BPOs I am usually guided by past similar sales and current listings, and I usually go by cost per Sq .ft.

Here are some recommendations for you:Find and connect with other BP members that are in your area: http://www.biggerpockets.com/meetSet up keyword alerts to be notified of the topics that interest you: http://www.biggerpockets.com/alertsRead Beginner’s Guide: http://www.biggerpockets.com/real-estate-investingCheck out BP Podcasts: http://www.biggerpockets.com/renewsblog/category/podcast/If you wish to tag someone in the conversation on the forum, type @ followed by their name and then select the name of that person which should appear below the comments box.

It has helped guide me in a better direction.

Here are some recommendations for you:Find and connect with other BP members that are in your area: http://www.biggerpockets.com/meetSet up keyword alerts to be notified of the topics that interest you: http://www.biggerpockets.com/alertsRead Beginner’s Guide: http://www.biggerpockets.com/real-estate-investingCheck out BP Podcasts: http://www.biggerpockets.com/renewsblog/category/podcast/Wishing you the best!

I'm sure you'd do fine if you study and buy a study guide for your state.  

Make sure to read the Beginner’s Guide: http://www.biggerpockets.com/real-estate-investing

I have been imagining building my sales website (buyers guide, community pages, IDX integration, home valuation page, etc) on MyOhioProperty.com and then building Evolvedproperty.com to give details on our services including making cash offers on homes, renovations, and our homes for rent.

Check out the Ultimate Beginner's Guide to Real Estate Investing:http://www.biggerpockets.com/ultimatebeginnersguide.pdf