Buy, use once and sell it will have a significant cost. You're at somewhere around $3500 on a 150 point contract assuming using 300 pts even ignoring any lost value on the contract for the RTU being shorter and the used points. That's simply closing, dues on the points used and sales commission. I would guess that approach would cost about $5K on 300 points used and add the risk of ROFR buying in and the aggravations of selling on the back end. IF you move it to 400 points the cost goes up about $1000 more. You'd probably need to use 400 points just to break even compared to renting. The underlying premise was my reason for questioning whether you'd go more than this one trip. While I think every third year is workable for some situations, normally every other year is my cutoff for whether buying is reasonable. But in this case every third year might put you where it'd be reasonable, or even if it was every 4 or 5 years, one could rent out in between.
Assuming 400 points for the trip in question and a studio every few years, it might work like this. Buy 120 points resale and 25 retail with an April or June UY (assuming that'd be good long term), bank the 2017 points added to 2018 and borrowing most of the 2019 points. Rent any points that you couldn't bank to 2018 UY. Bank the 2019 points to 2020 then use or rent them going forward as applicable. That assumes you could get a good value out of the retail perks, if not, just buy 150 points resale which might save more than the retail purchase would anyway. I'd discourage the transfer route due to the limitations of booking. The other benefit that owning gives you is access to special view types like AKV value or BWV standard for a single resort. But I wouldn't buy and sell just for the one trip.