In addition presuming you had a 30yr loan.  

You on the other hand are not looking for a profit since you presumably already made it and just want to be made whole.

California is yet to update it's meth clean up page, but it does seem to contain a contamination level of 1.5 micrograms per 100 square centimeters as a standard for presumably the max amount of residual methamphetamine.https://www.dtsc.ca.gov/SiteCleanup/ERP/Clan_Labs....For cleanup, there are lots of other state sites, e.g.

Now in this same situation lets presume you have a lot on your plate that will be sold next tax year thereby increasing your income to $100,000 pre-tax.

Presume this deal is to purchase both sides of a duplex and the well is not on the subject land so he can disconnect at property line.

With that I presume you have significant student debt, but also a big sword (high income) to attack it with.With a high income, plan on living well below your means for a few years and kill off the student debt.

I presume you mean the state board of realtors contract.

The owner has missed some payment in 2015 and presumably 2016.  

Also, presuming 1% increase in value annually, that's only 5% over that time.

Rather, you are moving your money from a vehicle (savings account presumably) that likely earns you 1-2% interest per year to an asset (rental property) that has potential to earn you 12% CoC year 1 according to your calculations.