Yes miners are very noisy, but it won't penetrate the wall of your garage upto the neighbours house, and you can put in sound absorbing curtains over the wall to reduce the noise. Secondly due to increased advancement in technology, new type of models will come out faster but it won't make your S9 obsolete it will just make it slower in competition and you can always buy new models and add them to the current rig to balance the investment.
Pools can be selected manually all the times. And it is always advisable to switch your pools every alternate day as you may end up with finding a block into another pool if it saturated. The rate of bitcoin will not affect your ROI because you will not always find the block every other day, it can can take few days to months with single rig. It is not that profitable as I mentioned already.
Thats all from my side, and one more thing, try to talk with your neighbour about mining technology, who knows they get interested and you can expand your rig with them and share big profits. (Just suggestion )
Thank you everyone for your advice, especially Darthmaul for that detailed insight. After thinking it through, I've decided that at this point I will give up on the idea of mining. It still seems very attractive to me in the long term, like over the next 10-20 years but with only having enough resources for one rig and not a great place for it, I'm putting it on hold. Maybe I'll just buy another bitcoin with the money I have left over, or maybe further explore carlfebz's suggestion and focus on ETH mining (although I have no idea what a GPU even is at this point, so it'll take some more educating on that front:) ).
Thanks again.