Hey there @Frederico_Loco
Coming from Live 8 and been through versions 9 & 10, I can assure you that Live 10 has got some really great features & enhancement comparing to Live 9, so unless being very sure to have the option to upgrade this license to Live 10 ( best way is to check with the seller & Ableton's support ) I won't do it that way. Live 9 is maintained but not upgraded anymore by Ableton, so if you can't upgrade to 10 with this 2nd hand license, then you're stuck with version 9.
There are other ways to get started with Live, one is to get the intro version to start with : it's priced GBP 69 / EUR 79 and it's a good way to get Live 10.
Another way is to get a Live Lite license when buying equipment from some manufacturers, I don't know if you already own an audio interface or if you're planning to get any midi controller later on but for example Focusrite & Novation offers good quality & fairly priced audio interfaces & midi controllers that include an Ableton's Live Lite license. Once you register your interface you also will have access to Plugin Collective and get free 3rd party plugins or deals each month. Later on you can upgrade your Live version by Ableton, they have sales ( most of the time 20% off ) from time to time like black friday, xmas sales...etc.
More about Live Lite here ( be sure to click on the "Features Inculded" link on top of the page as well.
Now in any case, if you plan to buy a second hand license, be sure you do it from someone you can trust and follow this Ableton's guide line about this, best way is to have the seller asking for license transfer eligibility & upgrade possibilities to Ableton via mail including you in CC, more about this here.
Hope this could help