Hello and welcome!
I have kept a 20 gallon tank for 3 years now and it is very low maintenance. I do not do water changes very often and do not need to clean the sides. Now this is a very established tank so it got to this point very slowly. For the lowest maintenance tank go planted...heavily. I have alot of plants and they grow really fast but also take care of the water. Now you might not hear the same from others this is not very common I have heard because I do not get many problems! I was/am very lucky. My fish are great(only have 9) which is not a huge bioload for my tank and only 3 types of plants that grew very fast. Sword plant(amazon I think and I believe it split into two now) vallisnerias and Java Moss
. All common all very nice plants. But you will need a nice lighting system and maybe a CO2 thingy(I don't) but the rest of the members will help you out more but really the key thing here is to have a huge amount of patience. Keeping a system can be easy... or it can be a nightmare but most likely easy if you follow a few guidelines.
1. and most important. WAIT FOR THE CYCLE. The most common mistake in beginners is you don't wait. You will want to wait for the cycle to happen first(Plants will help) if you do not know how to look for a cycle. The main thing you need is an ammonia test kit. Test for ammonia every few days until it spikes up then do a water change. You will also need a pH test kit and maybe a few others. Go with API test kits for this.
2. After the cycle don't go crazy buying fish this will cause your system to get too much of a bio-load at once and might become a nightmare. Start off with 1-3 fish depending on what you are getting.
3. Weekly water changes after the spike will help keep most of the parameters in check. Do ~10% every week or ~20% every two.
4. Be prepared for what you are getting. Don't buy a fish you don't know anything about. If you are making a community tank then look for the community fish section at your LFS or ask a worker.
If it is going to be a cichlid tank wait for others to help you because I do not know much.
If you follow those you are in good shape for a tank. Don't be discouraged it is alot of fun having a tank and very pleasing. Water changes do not take much time neither does testing 30min max every time for me at least.
Good luck. And if I forgot something or I have been misinformed myself then please someone correct me or add on.