Here is my recommendation. Do you research on battery and motor replacement. There are plenty of information here on this forum. Search the old and new thread.. Obviously this will be a big purchase and I hope you would take the time to do the research as oppose to reading a few comments here. There are people on both sides (people who own TSLA and those who don't) who will steer you one way or another for their own interest and not yours. I would be super wary for people with a lot of likes or new users. The ones with a lot likes are probabaly just sucking up to anything to get a lot of likes. The new users are probably just people who what to short or pump the stock.
That being said, there are a few threads you can read up which is a recent development because of the warranty just going out for the cars you are looking at. From my analysis and my own experience of my model s here are a couple of things to know.
1) older 2012 model s are pretty hard to self service. 12V/cabin filter replacement is much hard than it should be are some examples. This is mainly due to tesla putting things together last minute to avoid going bankrupt in 2012. The newer model s 2015 and newer are much better thought out in terms of serviceability. There is alot of things you can do yourself on the newer model s.
2) battery will be a hugh issue IMO. Recent threads (plural) have it quoted at $20K for a new 85Kwh pack or $15K for a remanufactured pack. And more if you want the 100Kwh pack assuming it fits in your car and they offer it to you. And without warranty, you will be on the hook for it. So if you were to buy, know this is a possibility, a high one IMO, because battery wear is cause not just usage but also time. And if this is the original pack, it has for sure seen 8-9 years of time even if it was lightly used. And know if 1 out of the 7000 cells or so fails in the 85Kwh pack, your whole battery is dead. That is all it takes. Read the other threads about alternative fixes for the battery problem, but IMO none really fix the issue and you can have the problem again.
3) motor and drive train. Again look at the threads on issues for model s, but the older model s had a lot of motor drive unit issues. If it was fixed on the model s you are looking at, then it shouldn't be much of an issue later to you. Again it probably has to do with tesla just putting things together hastily in 2012 to get the product out and had a lot of bugs in hardware and software drive train. The risk for you is usually this problem comes up in hard acceleration and if the car wasn't used much, it might have not seen a lot of hard acceleration to cause the issue for the previous own to replace for free before the warranty expired. Something to keep in mind.
4) minor issues here and there again attributed with older model s. The newer model s seems to be better put together using higher quality and lesson learned from the older cars so it is much more reliable in terms of small issues. Again since the car you are looking at has low mileage, the previous owner hasn't gotten enough usage to flush out all the issues during warranty period. It will be expensive to repair because tesla servicing isn't cheap. There are online videos to fix someone someone stuff yourself so there that.
Personally given all my research up to date, I wouldn't touch the older model s due to all the risks and potential reapir cost down the road with an out of warranty car. Now if you were to say I can buy the car for less than $10K then maybe I'll think about it. Anymore, I'm out. That being said, I have very low tolerance for risk hence why I need it to be lower than $10K for me to even think about taking on that risk. You might have a higher tolerance for risk and decide I'll take the chance. Everyone is different here.
Best of luck on your research and decision.