They are business credit cards which report to different agencies than your personal credit, so it wouldn't affect your personal status at all.

Personally, I'd never buy the biggest house, or the most expensive house on the street.

Quote from @David Eyal: This is actually very simple: don't get involved in personal issues.You offer them a renewal.

If a buyer has good credit he can get a personal loan to buy a property, and hence “nothing down”.  

I have locked up one deal off the application and have offered in person on 2-3 other deals.

you mention the person who is complaining is now and living in an efficiency unit (to me that has everything in it-ie fridge, stove). 

I would prefer the risk of a renovation to upgrade a building as opposed to location risk with a high risk tenant pool. 

We took this approach because even though the house is an STR it is also one we want to use as a family a couple times per year, and we feel we have our own personality as hosts, so we were particular about what we wanted. 

I  would look at your town regulations and see also if they have any unrelated persons ordinances and what they say about boarding houses. 

I gave them a lease in person to review and sign (I gave them the lease first as they mostly speak Spanish and the lease is in English, so I wanted to give them the time to read it).