AdamsCreek, don't think that you would be able to come out ahead on the buying then selling the bull in 90 days or so. Seems when we need something we always pay premium for it, then when it's time to sell, don't get back the worth. If you couldn't lease a bull from a neighbor, what if it is a bull they are thinking of selling in order to get new genetics for themselves???? Then you would probably be able to buy for cull price and then not lose when you sell. Since you know and get along with the two neighbors at least, I would certainly explore that avenue first.
Do the neighbors run the bull full time with the cows or only for a specific time frame? If full time then it might be a better chance to get it for a 60 day window. Also, you might want/ need to change the timing of how you manage the cows if you do go to leasing. Maybe later calves, and sold at lighter weights or kept longer and fed some for heavier weights....we have gotten very flexible here now that we have more numbers and sometimes put the calves on feed after weaning to hold until the market is better....but we have a whole different operation due to the fact that we can run 1 c/cf pair for every 1-3 acres instead of every 5-10 acres like your weather dictates. But we also make and feed alot of hay; we also do alot of rotational grazing and just moved 30 c/c pairs to pasture that was rotated off of in July, and will feed them for at least a month if no deep snow. They have 5 rolls in front of them and only see a few even wanting to munch on them so know that they are doing mostly grazing of the dry grass. And we will open up 2 hayfields that were only cut once so as to extend the grazing, which we will do in about 2 weeks then move them out again in mid-march so it doesn't ruin the fields when we start to get some rain and all before growth starts in April.
Too bad you aren't closer, we usually lease a couple of bulls every year and are glad to let someone else feed them for a couple of months...