End the accounting with the admonition of where they need to send the money they owe you.This will keep them from seeking out an attorney to litigate the matter. 

With the exception of the roof, just about every part of the house needs to be rehabbed (kitchen, bathroom, floors, windows, foundation, termite treatment, paint, plaster repair, insulation, electric and plumbing update) whether I want to preserve as a SFR or if I wanted to sell without a loss.I'm starting to wonder if makes sense to just tear down and do a new construction.

It's a bad idea to lease option to seek out lease options from preforeclosure sellers. 

If you built the garages, installed the pool, etc without permits and inspections, you'll have many more problems with getting those passed by your township than you may think.The solution I would recommend is to have your parents refi, put the property into a trust, you can be a co-beneficiary, and when you can afford, give them whatever money you have agreed to and have them quit claim their beneficial interest in the trust to you.I am a realtor, not an attorney, so please seek out a qualified attorney to get you set up. 

Section 1031 in the U.S.A. is considerably different and allows you to exchange (upgrade) assets.I would also disagree that having four residential mortgages in your own name precludes you from seeking additional ones from conventional lenders.  

Engage the local municipal and state governments who are seeking and redistributing these grants.

Investors who are in this position should seek a full understanding of the government's role in a situation like this.

That treatment makes it less porous but not sealed from water damage.

Is this an opportune time to seek out partnerships that are optimal for the moment.Or even better, how can you use generosity for those who need it most during these unprecedented times to create a lasting and meaningful relationship?

@Dillon Hutsell It is great that you are seeking this type of advice at such a young age.