You start paying MFs from the day you buy. So, whether you buy a Feb UY or a Oct UY, if you buy today your dues will be prorated (340 days of 2019 left). You get points for whatever UY you are in (everyone is in their 2018 UY right now) so would not pay any dues on the full 2018 points they receive.
This is something I feel many people do not calculate correctly when comparing resale vs direct.
If I bought an Oct UY in September 2019, I would receive all 2018 points forward and only pay 4 months of 2019 dues.