Not sure what to do about this. Our boy is 5 years old and has lived his whole life in our current ground floor flat with garden and cat flap. He goes in and out as he pleases and is partial to the occasional mouse (!)
Unfortunately we are moving to a ground floor flat with a communal entrance and communal garden so no possibility of a cat flap. We struggled to even find somewhere ground floor we can afford so this is the best we can do.
What shall I do with him when I'm at work and overnight - shut him out or in? Presumably I will have to have a litter tray in case he needs it? He will be able to come in and out of a window but we can't leave it open all of the time as we're in London.
My MIL removes a house brick and places a cat flap over that. It doesnt look pretty but usually she has her sofa next to it so its sort of hidden. Then when she moves she puts the brick back and a little bit of plaster.
You can fit flaps in windows. I'm guessing you're renting? Assuming it's the ubiquitous UPVC double glazing, you can get a glazier to make you a new double glazed unit with a cat flap hole to attach the flap to. Keep the original double glazed unit to put back when you leave.
If you are buying I would get one put in a wall somewhere or window. Ours is going in out back door which is glass so having to get a whole new piece with a hole already cut into it for the flap. It's not cheap but it's preferable to leaving a window open
And don't forget to make sure it's a microchip flap
When we got our back door replaced, we gave the Sureflap to the firm and they fitted it all nicely for us in the corner of the door panel furthest from the handle so not even a gorilla could reach across and up to unlock it. The alternative would have been a patio door with a flap which would have cost ££.
I have had outdoor cats without a cat flap, but depended on being able to let them out for a little while each morning and evening and they stayed in during the day. And in my childhood we never had cat flaps, just put the cat out in the morning and let it in at night. But I think we pander to cats more these days!