If the sales price is $850k you will need significant down payment to carry the DSCR loan on $5300 current rents...check in with @Joseph Chiofalo  as DSCR loans 5+ units are typically a bit more difficult to place as well. 

For example: If your credit limit is $500, you want to carry a balance of $45.00.

Many of us have been investing for decades, always carried reserves, never had more than 1-2 months of vacancy, and never had rents decline (all intentional and controllable based on what and where we buy). 

I also know that doing a 1031 exchange will enable us to carry all of the proceeds from the sale as a deposit on a new property.   

So, even if 1 property has excessive expenses in a given year the other properties carry it.

The cost of purchasing the house, rehabbing the house, and extra reservea and carrying costs during that time.Take a nicer part of Baltimore, I'd probably want $350-400k liquid.

Also a seller concession is a good tool to reduce closing costs and carrying more than necessary on the primary. 

@Michael HyunSeller financed properties usually have some type of motivated seller, or else they would just list it and not worry about carrying the note.I've bought and sold on seller financing, and very few sellers elect to seller finance, unless they have to or are looking to defer taxes.Welcome to where we are in the market cycle.

BUSINESS carries risk.

I buy most of my notes direct from seller carry and inherited private notes