I've bought a half cage, olympic bar, sets of DBs and plates, racks and bench, for my home gym, from We'R Fitness. Sounds like it is what youre looking for. It's at kota damansara. Imported but decently priced

Quite a lot. It's a room on it's own but it's enough to contain each of those, with a cable motion strength machine, and still have room for two people to be moving around and working out in. Just make sure you have planning with the measurements, placements, your movements around, and to have absorptive rubber flooring especially , then you would not have much to worry about.

Just a slight renovation. It was a spare room at the ground floor. Only opened up the back wall of the gym room and placed a full sliding door since it is connected to the garden. Just so I could open up the sliding door, in case I need more space.
If you place it upstairs, I reckon that you should have a good, thick rubber mat on ur gym floor, else it's going to be loud downstairs and possibly vibrate what's on the ceiling downstairs, such as the ceiling lamp, if you so happen to drop the weights. And yeah, definitely will be an issue with kids around if on the family room upstairs, considering it's an open space . You can look for all-in-one of sorts too, to save space. Something like this https://www.tytax.com but I'm not sure if we have that here in malaysia. U can try asking those distributors if they carry similar equipment like that