Are you being pestered, by any chance?
I did the same to my DM 25 years ago and still obsessed with peeing about with fish tanks.
First of all, how much space do you have for a fish tank? There are lots of beginners' tanks and children's tanks that are no damn good for anything apart from holding water. The absolute minimum I would consider would be 45 litres, and that would limit your choice of fish pretty severely. Something like 60 litres would be easy to maintain and there are lots of small fish that would be fine in there. If you need help with specific filters etc then just ask.
Tropical fish are no harder to keep than coldwater fish, but there are a lot more to choose from so you need to be more careful about choosing.
Once you've got the tank set up and everything running, you need to do a fishless cycle. It's not complicated but it takes aaaaages. DOn't bother buying any of the hundreds of products available that claim to speed up the process, most of them are rubbish.
You'll need to get a water test kit and learn the basics of water quality and the nitrogen cycle- there's not that much to learn and it's not that complicated but it's v important.
If you do a fishless cycle, stock the tank carefully and keep an eye on the water quality, then a fish tank is very low maintenance. So it's worth doing it properly from the start.
HTH a bit! Have to dash out so if any of that doesn't make sense, just ask and I'll be around again later.