If you are looking at longevity, buy new, not used.
That $100 GTX1060 will be the 3gb version which is slower because it has fewer CUDA cores than the 6gb version.
You can only buy a cheap psu for $50.
If you care about long lasting, do not buy used.
A cheap PSU will be made of substandard components. It will not have safety and overload protections.
The danger is if it fails under load, it can destroy anything it is connected to.
It will deliver advertised power only at room temperatures, not at higher temperatures found when installed in a case.
The wattage will be delivered on the 3 and 5v rails, not on the 12v rails where modern parts
like the CPU and Graphics cards need it. What power is delivered may fluctuate and cause instability
issues that are hard to diagnose.
Do not buy one.
If you buy a psu, consider it as a long term investment.
Plan on $100 or more for a quality 550w or better unit.
I like the seasonic focus units with 7 or 10 year warranties.
You might also look at the newer GTX1650 cards. They are a touch faster than gtx1050ti and are the strongest cards that do not need aux power.