Next, adding interest to an underlying loan, several issues, but your interest rate won't match the principal owing on the underlying mortgage this makes tax reporting and borrower disclosures difficult, beyond the financial scope of any small investor without a loan compliance department. 

You can get very reliable and accurate contact info for principals using LexisNexis or TLO. 

When selling to you as a FSBO and you are a principal in the transaction, no realtors are needed.

I am a principal party in a valid and assignable Purchase and Sales Agreement which allows me to purchase 123 ABC St.

If you have 3-5 years to force appreciation and pay down principal you can refinance when you're ready to move out with a better LTV and cut out PMI to help cash flow. 

Ask the owner for a copy of his monthly statement which will give you a breakdown of his principal balance and an estimate of the amount owed to the bank.

Keep in mind that your also paying down the principal and building equity Good luck!

I realize the extra cashflow, and I can always make additional principal payments.  

If your timeline is 1-2 years then money market or CD will be your best vehicle to park your money.You don't want to risk your principal in anything riskier with a short timeline.

@Khalia Luff,As an agent, you will list the property for sale through your brokerage, however most brokers/Principal brokers will negotiate either no fee on your end to list it or at most (in my case) I cover the royalty fee (we are a Century 21 affiliate, so we pay 6% on any commission) and that is all.