The rental is currently unregistered with the city, so I would like to end their lease, do a little upgrade and get the city's rental license before renting to a new tenant.

Calvin Lee,You won't really find a 7 cap Dollar General in a strong suburban to urban core location unless limited years remaining on primary lease term and mostly cash deals or very small financing.The brand new Dollar Generals with upgraded construction all around in strong suburban to urban core areas tend to sell for 5.75 to 6.4 caps with new leases in place.The 7 cap new Dollar Generals tend to be in crap areas weak suburban to rural and cheap construction and many times on septic systems instead of county or city sewer.Every once in awhile in a strong location there might be a 7 cap with 10 years left on a high end Dollar General at 3 million in price or up.These have no rental increases in primary lease term so year over year your income dollar becomes worth less and less.

After you do those minor fixes, it should appraise closer to the market value of $450k, especially if the upgrades add value. 

Recently upgraded to pro account and tried using the "find deal" tool.

Your savings is good, but your income won't support that many properties if you do them wrong and need to carry 15k min reserves for each one.Focus on what the next property should be, maybe upgrade to a two-family and see how that goes.

In that example, I was imagining that the investor made upgrades and improvements AFTER closing, either with their own funds, a personal loan, credit cards, etc.  

NY Market is very competitive, so getting a good deal might be worth the investment of being flexible with your preferences or any upgrades needed on the property; cheap houses are houses that need work or problems that need to be fixed. 

A distressed owner isn't about to upgrade and repair.

Renovating 4 units and upgrading exterior What was the outcome?

I'd like to use these to upgrade into something much larger in the next 2-4 years. 20+ units.