I'd definitely consider the new PM route.

It took me all of five minutes to find multiple examples of other BP members who have had their notes called by the bank based on the Due on Sale clause:https://www.biggerpockets.com/forums/50/topics/386043-bank-called-my-due-on-sale-clausehttps://www.biggerpockets.com/forums/83/topics/190300-due-on-sale-called-what-nowhttps://www.biggerpockets.com/forums/311/topics/183825-due-on-sale-clause-was-called-by-bankKnow the risks if you decide to go that route.

Even though we were going to flip it, we realized that the lease option route would produce a greater overall return and cash flow in the mean time (about $800 of cash flow a month split between my partner and I).  

Most people don't go that route.

They tell me to go the traditional route and work under some company and build it the long way.

Taking the slower, and smarter, route will only make your dream car that much sweeter.

That route puts me at 30% capital into the house, trying up a ton of money for about $275 in cash flow a month.

If I cant make that work, I'm going to try the marble threshold or travertine sill route like in a bathroom. 

Any recommendations on which route to take the money out?

Definitely weigh your options and understand the conventional route is going to be less expensive in both the short term and long, but there are other options if you're in a jam.Stephanie