Let's say stocks are normally a cleaner and more sophisticated way to invest vs average real estate stuff. 

Getting a seller to leave existing financing or carry a short-term note doesn't involve jumping through hoops to get hard/private money or institutional financing and it's much easier and cleaner this way. 

(if you are design-challenged, please have a woman/designer give you advise: it will pay long-term)--also make sure your house/units smell wonderific/seasonal (apple cinnamon/santal wood/ebony)-a welcome package would set you apart also (less then $10 at dollar tree supplies: toilet paper roll, cleaning paper roll, toilet plunger, cleaning brush, cheap shower liner, soap dispenser, all-purpose cleaner container, couple garbage bags) + box/pack of water bottles in the fridge-you do not need to buy stainless steel appliances, but do make connections with local used appliances store (they may have warranty in place, and know the appliances which make do /resists in the area). use white or black, simple and reliable type-find out which appliances tenants usually bring with them in the area-DO NOT implement the Section 8 Bible books advises (but do read the books).

Good wallpaper will be a real pain and come off in small pieces, leaving lots of prep work for you if you have a lot of scraping to do,  If that is the case just replacing the Sheetrock is easier and cleaner result.  

You make it a fresher, cleaner and more welcoming property.

I'm thinking rehabbers want a cleaner look, but maybe it is just penny-pinching.

It's not illegal for a mortgage company to fund a loan sold by an owner, but it needs to be fully disclosed.Your MC will need an office, a sign on the door, a HUD sticker, a bank account for escrows and funding, a telephone and if servicing a toll free number along with local office complaince issues, it's not that hard.You could have an independent MO originate seller financed notes as well, that's another strategy but I believe in the current environment this would be cleaner.

I can put down kitty litter to soak up the majority on top then scrub it with purple grease cleaner and finally power wash it.

Put them everywhere,,,they will only use so many anyway.You NEED grounded for some items like computer, some appliances, generally a vacuum cleaner, modern tv's etc. 

Institutions on larger properties can get very special relationship financing from lenders not available to the average investor.On the retail properties I usually work on properties 1.5 million and above but NNN deals tend to be cleaner than value add apartment properties that suck a lot of time in the low price range to close.