With your salary (and assuming no other outstanding debt) you'll want to keep our mortgage payment to ~$1400.

How do I go about paying back the outstanding loan?

On the positive, that area has outstanding historical appreciation.  

And the sad fact is that Baltimore City would rather have the property sit vacant than negotiate or waive the outstanding amount due.As has been said here and elsewhere in Bigger Pockets, there are investors who know how to make money in the D-class rental areas.

Are you more comfortable having no debt at all (including properties), having 20+ properties with outstanding loans and HELOCs that fund other purchases, or somewhere in between those two? 

And do you know......ALL mtg loans are simple interest....which means your payment each month contains an interest portion based on the outstanding principal, and the interest rate, for That preceding month.

Please note that per the multiple loan rules, the amount of the loan must be reduced by the highest outstanding balance of any other 401k participant loan over the prior 12 months (regardless of whether such other loan is currently outstanding).Monthly or Quarterly Payments: The loan must be paid back in equal monthly or quarterly payments of principal and interest.Interest Rate: The interest rate is equal to prime plus 1% (or CD rate plus 2%) and is a fixed rate that is set at the time that the loan is taken.Term of the Loan: Five-year term unless the proceeds of the loan are used to purchase a primary residence in which case the term of the loan may be up to 30 years.First Payment:For monthly payments, the first payment that would otherwise be due is delayed until January 2021 (e.g. if the first monthly payment would have been due on May 15, 2020, it will be due on January 15, 2021).For quarterly payments, the first payment that would otherwise be due is delayed until the first quarter of 2021 (e.g. if the first quarterly payment would have been due on May 15, 2020, it will be due on February 15, 2021).EXISTING LOANS:The CARES Act which was enacted to provide relief to individuals impacted by COVID-19 allows for increased 401k loans and more flexibility for repayment of these loans.Specifically, you must be an individual who meets one of the following conditions to demonstrate that you have been impacted by the crisis (and it will be your responsibility to retain documents in your files that demonstrates that you are a qualified individual):Individual who is diagnosed with COVID-19, with a CDC-approved test;Individual whose spouse or dependent is diagnosed with COVID-19, with a CDC-approved test; ORIndividual who experiences adverse financial consequences as a result of being quarantined, furloughed, laid off, having work hours reduced, being unable to work due to lack of child care due to COVID-19, closing or reducing hours of a business owned or operated by the individual due to COVID-19; or other factors as determined by the Treasury Secretary.If you meet the above conditions:You may delay making any 401k loan payments due between 3/27/2020 and 12/31/2020.You must commence making loan payments in January 2021 (or the first quarter of 2021 if your loan payments are due on a quarterly basis).If you elect to delay making such loan payments, the term of your loan will be appropriately extended.

They said the cost per month is 1% of your outstanding balance, not the overall limit.

Reasonable Rates, outstanding explanations and always looking out for my best interest. 

This is called abatement and can be an unwelcome surprise if it happens to you.We recently had this happen to us not because we were being negligent in our landlord duties, but because there were outstanding maintenance requests to the previous landlord that caused HUD to stop paying until it got resolved.