usually an eviction is done against "named tenant" and "any unknown occupants" or something similar. this gives you the right to evict anyone living in the property. otherwise, you can only evict the named tenants and anyone else living there is allowed to stay (and let the others back in).

Honestly fear of the unknown and messing something up is why we are trying to avoid portfolio loans that and we do not know much about them. 

Somebody wanting to sue for you backing out of a bad deal or accusing you of selling them a property with defects like unknown termite damage).

Knowing when to let go e.g. find a building that is reg-tagged, rather than just having electrical violation. too many or unknown issues.

So by paying the seller $75,000 to finance the deal he is saving himself $500,000In ten years he's still going to have unknown financing costs when the note comes due. 

At the end of the day you can’t have an unknowns animal, medical or not, on the premise in case you or officials (gas company etc) need to enter the unit without the tenant home.

He installed a cheaper unknown brand throughout our duplex.

If you underwrote this deal very conservatively, and have $100k+ extra dollars in your budget (that includes a contingency for all of the unknowns, possible continued inflation, a surge in materials & labor pricing, longer hold times, etc.), then it could work by hiring a well qualified GC to handle EVERYTHING, like @Jonathan Klemm & Quality Builders, for example. 

This should be much less in a build verses as renovation where you find unknown preexisting conditions.

Unknown people on the lease?