We got two young adults (bro/sis) from the CPL in May.
They have the run of the house except the Utility and the Pantry .....cats don't like closed doors so are constantly trying (and often manage) to get in there .
They have a micro chip activated cat door which is a massive bonus to them, they like being able to choose . We bring them in at night (they know the cal for supper) When they were indoors to get used to us , going out in the garden was like a military operation.
Our trays are in the cupboard under the stairs -with a standard cat door . I've used Cats Best litter since they arrived , it does track but it's soft on their feet and helps with odour control .
They're tidy , love routine . Not lapcats but the like to be with us.
My DC are late teens so we have 4 looking after them. They're family cats so we all do the food, litter, water.
They leave fur everywhere , even though they're short coated .
We've had no little dead presents (yet) though our old cat was a prolific hunter .
Factor in prices-
the food , the litter
insurance
vet bills (your insurance will likely have an excess)
the cost of the cat itself (ours were £80 each but they were chipped./neutered/vaccined which we'd have done anyway so they actually cost less in real terms)
Holidays/boarding
the cost of replacing things (our last cat shredded our stair carpet through to the wood!)
They sleep all day (my DC are on holiday from Uni/6th form so keep an eye on them) then they run round in the afternoon, go out in the evening. Have a Mad Half Hour and potter round the house at 2am.
The number of times we've nearly tripped over them on the stairs 
Mine are fine with my teenagers but a small child might get upset at the claws , though they'll walk off if they aren't in the mood for fuss . My DC know to read the cats' body language (or suffer the consequences . The cats tell us plain as day )
Your neighbours might not like them if they use their gardens (though my cats tend to use the trays indoors .)
You'll be commiting 15-20 years to them.
I look at ours now and cannot imagine our house without them.