They keep their unit spotless and have nice furniture.

.- Closets: sweep, mop or vacuum- Floors: sweep, mop or vacuum PaintingUse drop cloths to protect furniture, floors from paint -Protect and mask necessary finished surfaces including door knobs, hinges, bathtubs, showers, cabinets, electrical outlets, fixtures and windows-Caulk all joints at doors casings and jambs in order to maintain a sealed surface-Caulk all joints around the windows where the window meets the drywall Patch and/or repair of minor wall and ceiling blemishes prior to the application of paint-Apply primer coat-Apply 1st and 2nd coats (Two-tone paint available)-Remove all masking from doors, windows, baseboards , walls, hinges, floors, etc.

I've seen garbage (mattresses, furniture, etc) piled up around the dumpster. 

Dark stains like walnut are richer and add elegance as well as help to anchor and showcase furniture better as long as the furniture is lighter tones and color.

And I am a wood worker that builds furniture etc so I thought I knew what I was doing.  

There were a 5-6 pieces of solid wood furniture that may have brought in a couple of hundred dollars each, but we didn't have time for that, as we are in the flipping business-  not the resale furniture business. 

The vanity itself was a sink sitting on a handicap toilet chair* Sheetrock patch made up of packing tape and sheetrock mud* P-trap being held up by a leather belt and mostly consisting of duct tap

I've had tenants that couldn't pay the rent because after they moved in, decided to rent a house full of furniture and appliances, including an iPad .  

If the unit has good air flow, such as you would find with a forced air HVAC system, it will lessen the chance of moisture build up.If the tenant had blocked the sliding glass door and surrounding area with excessive furniture, boxes, or clutter, then that could lead to moisture getting trapped.

First, I'll be furnishing the place to the tune of, say, at least $20k in furniture.