Personally, I prefer to see the material taken for recycling by those guys than hauled to a landfill.  

Most simple thing, do math for both hypothetical situations and see which one brings you more money, consider rent you will pay, and the interest you will pay for heloc for cash out, and whether you can finance the new properties or not.I personally would never sell a SFR in an appreciating location so I can milk it during every cycle.

Thus the recycling side of it is becoming more profitable...

I guess they just recycle their capital for each sfr and then replace their capital with the bank's capital.

You are confine to the fields they provide for you which is very difficult.Most of their data out dated and they keep recycling it.

Some professional tenants will pay the rent on time but then milk the landlord for free utilities.

If you are trying to recycle the money, you are better off find properties that need rehab and using a rehab loan to fix it up, then you would refinance the property into a 30Y loan at the new ARV or just sell for a profit.

., has it been milked)?

Where I am (Southern California) many (most) municipalities regulate minimal recycling percentages, making haul off and dumping more involved and more expensive).

Have you tried Milk St Capital?