This would let you buy for 3-5% down and if done right, decrease your housing costs.

I'd also post notices and talk to other occupants to see if this has happened before.

I'm looking for help on how to word a notice that personal stuff must be removed and not be put back without offending anyone. 

@Nathan Caffero I would reiterate 2 things I've noticed in this thread: 1) Education and 2) Your personal goals.

It’s been great for the last 3 years, but the owner has since given us notice that they can no longer carry the mortgage and were looking to switch to a different fiance option.

If they had a verbal agreement with the last tenant,   and the last tenant gave notice or has officially abandoned per definition thereof  (you can look for things like them having cancelled their utility accounts, emptied unit of their belongings, etc)  then they can't prove anything and maybe you can use that approach.   

Can I simply give them a 30 day notice to evacuate my house or does the pandemic affect this as well?

He has my tenants number for giving them notices on coming by.

Unemployment numbers are decreasing.

And from my experience with appraisers, they wouldn't notice the crawl space, and even if they did, they wouldn't know what they're looking at.