Regarding your question about whether lenders will allow a seller's second, according to the Fannie Mae guidelines, seller financing is permissible as long as it's subordinate to the lender's first mortgage, but there are some important caveats to keep in mind.

Put the shoe on the other foot, you worked hard to own property that you care for and a renter is now subleasing without your permission. 

Easy way to not get scammedWe find people putting our logo on their documents and websites without permission trying to suck people in using our reputation. 

No eviction without permission of the court, though.

So no formal lease for the dumb kid that let someone move in without my permission.

For new leases, you write in the permission for the inspections as well.3.

If you had permission then it's not "adverse and notorious" against the true owners and you wouldn't be able to get title via AP.”22nd post on page 1 of the thread, - Adverse possession claims after being forced out of home.

Do I even need permission from the owner?

Our problem tenant is airbnb-ing her unit without permission.

You as the owner didn't give her permission to stay, so she has to go.