As a lender we don't talk about things like this a lot, unless specifically requested, because "exotic" mortgage options un-prompted make people think you're trying to pull some 2007-style shenanigans on them. 

Electric car tends to have shorter life than other regular car. tesla holds their value far better than any other car other than some sort of exotic.  

Then, it wasnt uncommon to get 25-30 offers on a hot property, with these zero down exotic loans by people that couldnt afford the properties in 2005.Come 2010, properties were getting 10-15 offers all cash. 

And even those not in the 1% are fronting in their social media by renting mansions and exotic cars for a day to do their videos. 

If the property is new construction that has passed all inspections, you can probably get away with $0 per square foot.If it's a property made out of asbestos and lead that needs to be torn down and you plan to use artisan contractors to rebuild a complex structure with high-end exotic construction materials, you could be looking at $1000 per square foot.So, I'd say somewhere between $0 and $1000 per square foot, depending on a whole bunch of details you haven't made clear.

In other words, you can give yourself permission to live larger and take more exotic vacations, etc. when your passive income affords you that lifestyle.

If I still had more money I would start adding more exotic/riskier strategies in smaller amounts.

Simple debt deals where folks get interest are a lot easier to figure out than more exotic equity structures where more assumptions need to be made.  

I suggest using the opportunity you have right in front of you -- a motivated seller willing to consider sub2 -- and not try to create something exotic. 

If you're looking for more "exotic" (non-conforming) financing, look at credit unions, smaller community banks, and maybe a good mortgage broker.