This is because instead of developing the highly targeted profitable sales, you’re spending your time servicing the marginal.

I have heard the target is at least 400-500 per month net positive cash flow based on 20% down.

Transforming SFHs into multi-units and targeting 2-4 units for value-add potential is a smart way to build your portfolio, especially if your goal is to qualify for larger loans down the line.If you're aiming to hit the 5-unit mark and unlock better financing options, here's something to consider:Leveraging BRRRR Strategy: You’re already thinking about the refi route, which is key.

CHA even pays more for "targeted" areas. 

Do I target a duplex/triplex or a SFH?

Buy the rock solid rental and get your appreciation, cash flow, depreciation, principal pay down, equity capture on a discounted by and forced appreciation gain for a well targeted rehab.  

The home is right across from a shopping center anchored by a Target, Kohls, LA fitness, and more.

Wholesalers often have properties at below-market prices, and realtors can help you identify potential deals in your target areas.

The question you are asking, and what your post indicates that you want... makes you a ripe target for a high priced guru to sell you their expensive mastermind or tribe membership. 

Make sure that there is enough room for investors, and attack those dealsIf you're targeting quantity, then maybe you need to have a lot more than 20 contracts at a time to make headway.