We've had 2 units rented long-term at our MTR rate which seems like a homerun to us because we have no vacancy, cleanings, turns, etc.

His were cheap to buy, easy to clean and are booked continuously, he has the HOA to contend with.  

i always thought that japanese make great tenants, respectful, clean, pay on time.

Also, does anyone use/have feedback on local Airbnb cleaning services?

An INVESTOR does not repair appliances, does not unclog toilets, does not paint walls, clean units, OWNER OPERATORS do those things, Business Owners/Operators do those things, NOT INVESTORS. 

2) Does old carpet bring the house value down?

A condition of the cash for keys should be that they don't leave behind dumpsters full of things.To me broom swept meant 100% free of belongings and actually cleaned albeit not deeply.

As @Charles Carillo said, you can make the most of that time, but most people just waste the 4-5 years and then end up doing something unrelated to their degree field anyway.Maybe look into a Trade School, like an electrical one....nice clean work that pays really well.

In their favor:As homeowners and landlords they should be more reasonable and take better care of the place.Steady income with SSI and willing to hustle when they need more.They are motivated to make it work, offering more and reasonable concessions.If there is no carpet there would be less impact by dog or bed bugs, if either go worst case scenario.Not in their favor:They may be renting as a temporary situation until they can find where they really want to live long term, so they may not be a long term tenant.They are not familiar with the neighborhood, other than school district quality, so they may not be a long term tenant.What I would look at more:How long have they all lived at previous addresses?

Since they are nearby, they would have local housekeeping and handyman contacts for cleaning and emergencies.