Just go to the shops is my advice. I recently bought some new computers and if you are like me the information on the internet will be too confusing for you. It is really helpful to talk to someone there and be able to play around with it before you buy
(Btw I bought two iMacs and I love them

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Some things to think about before you go:
- what do you have now? will you need to buy a new mouse, keyboard or anything like that? will it be difficult for you to get used to any new things?
- what will you use it for? you've already thought about that but it is good to be sure because they will ask you in the store.
- how much are you willing to spend?
if you are sure an iMac would be capable of doing what you want it to do I think it would be good for you. It really doesn't take up a lot of space which you said is important. There is just a screen, mouse, keyboard and one wire.
Moving an iMac to a new home wouldn't be too difficult but obviously moving a laptop would be much easier. Plus you can take laptops to school/university/work or where ever else you might need it.