Evidence of cats: smell, urine damage, scratching damage on your woodwork and on their furniture, pet hair (look under refrigerator and range and in hvac ducts and filters), broken window blinds, kitty litter box, cat food.... the cat itself! 

There is no such thing as an outdoor smoke detector. 

They could still try to nest in other places, such as cracks in furniture, but they will be much more easily seen by cleaners and exterminated.

The property is already fully furnished with West Elm furniture.

As others have pointed out, you could purchase a used one or even rent one from a furniture rental store for much less.If it were me, I wouldn't offer any concession the first couple of weeks.

We purchased the house in end of February and took about 2 months to repaint/fix a few items/decorate/and get furniture delivered. 

There is a solution and I am building it...a hybrid apartment/hotel located in the commercial district near shopping and entertainment with no residential zoning issues and with pool, gym, laundry, courtyard, and outdoor kitchen on site.

Not to mention the furniture. 

This would mean pools/hot tubs, game rooms, nice outdoor spaces, views, etc.  

Get real photos of the areas with the actual furniture.