I don't want there to be important things that I wished I had asked prior to joining them.

Probably best practice is to try to gather more information about the specific property and owner's situation prior to reaching out with an offer. 

The prior owners had a cat. 

She tells me that she was injustly placed in county jail prior to taking residence and that was the reason that the dog is dirty, full of burrs and fleas. 

You'll have an opportunity to review the condo docs prior to purchase.

@Daniel B.There will definitely be some taxes that you will pay as a result of the sale - the question is how much.You have some 'non-qualified' use when it comes to the 2/5 section 121 exclusion since you lived in the unit prior to having it as a personal residence.You may want to consider doing a 1031 exchange depending on what the tax hit will be.

Do they require your approval prior to repairs etc?

They could demand a replacement of the sewer line prior to approving the ADU application which means there may not be a choice of not doing it anyway.

I definitely didn’t plan on purchasing a roof within my 1st 4 months of owning the home... prior to purchasing, I had an inspection done and the inspector noted that the roof was fine for now and that it had a few more years of life left.

Saying 'no' to pets will drastically reduce your candidate pool, so you might shop for a pet-friendly house (hard floors, securely fenced yard).Even if you're cool with pets, you should meet the specific pets and have a good long talk with the candidate on that animal's temperament and quirks prior to agreeing to lease to them.