Any structure that was built as a single family that is now operating as a two family is suspicious.

In a small family run business you can also add back in items that the owners were paying for out of the business but had more direct impact on their personal lives and were not 100% necessary to run the business (vehicle, phones, HSA, etc), but be careful about trying to add back too many items because a buyer will get suspicious.

A contractor that won't pull permits is very suspicious.

Politely ask them to call you if they notice anything funny/suspicious going on with your property. 

I just always try to be conscious of the biases someone may have so I'm naturally suspicious.

They’re emails are marked spam and suspicious and look like phishing emails. 

You didn't mention any actual damage you didn't get paid for just some suspicious wear and tear.If you can prove they had someone extra living there you could issue a lease warning and evict if they don't correct the situation.

And others will give you a suspiciously low price. 

Came out a few months after covid first appeared, rather suspicious. 

Since they're not contacting us now I'm more suspicious of them and believe they may actually be responsible for the initial break-in.