Me and another guy scraped up $1,200 and bought a property from a guy for the outstanding tax liens on it. 

Typically, when doing an installment sale, does the seller (me) charge "interest" on the outstanding balance, or would I simply mark up the sales price to some fixed amount (which of course can be calculated using a target interest rate).thanks.

Yes Borrow Borrow and Buy i acquired, 16 doors in 18 months, when i was 22 all i started that venture with was an idea and a credit card, i had high paying private equity job so i had outstanding credit and good banking contacts, was making about 4,720 in cash flow but also think the bigger picture about the equity you build thats what i always tell the people i consult, and how much value your properties will gain in the next 5 years. 

(Security) The Total Principal of the PPFP together with the PPSP shall be secured by a Deed Of Trust to be filed......any default with respect to either principal part shall constitute a default of the entire obligation outstanding at the time of default.

His fleet of about 50 mid-range houses reflect 30+ years of refining what works for most investors who are neither dealing with luxury or low end rentals.

Because of that, I know I'm not going to get the outstanding ROI's that some get.  

Otherwise, the balance due will just continue to grow.Otherwise, consider a Cash-for-Keys surrender to get possession back with minimal losses (ie balance still outstanding).

The outstanding balance was $116,900, however the open bid was $124,167.  

Heck, once you start paying the whole fleet will be out there looking for you as it's easy money for them.

Outstanding principle balance is 118k.