a purchase thru disney, right now SSR resort, you have to purchase 150 points or more.
after that you may purchase add ons of 25,50,or more.
a resale, you can choose which resort you would like to be your home resort, you can purchase any amount of points, and then add on thru disney if you would like, but you have to pay closing cost thru resale.
renting points: you can have as many as transfers in as you would like, it use to be one but
dvc has changed that rule.
but once you transfer in and cannot transfer out in the same use year, but you seem to be more interested in transferring in.
a good amount of points to start out with thru disney is 150 with no closing cost.
and when renting points you have to be careful to make sure the points are good for your dates, and if you want to make ressies at the 11 month for a certain dvc resort you would have to rent points for that resort, example you want to rent points for the wlv for 2 bedroom and need to make ressies 11 months out you would have to find someone with wlv points.
and if you own at a different resort you cannot combine yor home resort points to stay at the wlv making the ressies 11 months out, you would have to wait for 7 month out to combine the points to make the ressies or use the wlv points for half of the ressies at 11 months and add your points at the 7 months.
just make sure you read the transferring rules.