The ones I've used are inflexible and provide almost no customer service, but they seem to work efficiently for someone who knows the process and is willing to take the risk.

My company also offers custom construction services to clients for their personal homes.

There are also quite a few teardowns with 1.2-1.6m customs going up in their place.

In my experience, it's short-term pain for long-term gain (because much of the revenue you'd lose from unpaid rent, property damage, premises liability claims, losing loyal customers, etc.) is made back.

I have never listed a smaller space before, but as an airbnb customer I have seen listings described as "private basement apartment with separate entrance" for example.

If you are versed in these matters, you can go directly to the listing agent to see the property and simply be a customer and not a client. 

Custom spreadsheets may be the best approach indeed in your situation.

If people don't have the traffic/customers or money to pay the rent in the short term it is more of a long term appreciation hold. 

I agree with Kyle, I haven't gone up in rents with existing customers, but I'm continuing to increase rent with a new customer to bring the property back to current prices.

It didn't turn out that way.There were several customers who can't pay, but supposedly had vast assets.