Make sure to ask for proof they're bonded & insured qnd that they have workers comp to cover any additional cleaners they bring with them. Not just because of damage to your property. If the cleaner is injured your insurance could be on the hook if they aren't. This is a more common concern then you'd think. I'd also ask them what products they use specifically and ensure they are actually following manufacturer directions so as not to leave residue behind. Especially on floors that can become sticky or slippery due to incorrect product application. Used to clean houses learned a lot of tricks but also saw a lot of issues and shady business practices.