24" diameter or better, lengths??? don't know for sure... they mostly work with black walnut but said they would be interested in any kind of walnut, this is for the mill in Portland, search for walnut buyers in oregon or washington, still waiting on the mills closer to me... Orygone is a bit of a hike with 6000 lbs of wood behind a tired f-250 and a bad tranny...
Sounds like an arborist COULD make money at those prices -- but when you get a call to remove a walnut, the caller thinks that they will also make money. Therefore, you may have to trade the removal cost for ownership of the log or logs. The owner might also ask for the receipts from sale of the logs, in order to get a cut of the profit. It would all come down to the deal you make with the tree owner.
Personally, I would add up all the possible commercial logs in the tree, noting diameter (at the SMALL end---that is the end that counts in log sales), length, and any defect (decay, large knots, wind-shake scars/cracks, forks, metal) and send the potential buyer this info plus photos. You can estimate all this from the ground, with some experience, or even better, climb the tree and measure with a tape. The potential buyer might give you an estimate of the value, with the caveat that they would still need to inspect the cut logs before paying anything.
If you assume you are going to make lots of money and have already agreed to remove the tree for free, you could lose :msp_scared:, in that you now have a lot of expensive green firewood.
What I would do: write a contract with the tree owner as a break even swap, with cash going back to the tree owner if you get paid more than some percentage over your costs plus business profit. Why? You need to offer to share the profit, because I have found most walnut tree owners assume that they can make money selling even one tree of doubtful value -- they are going to expect something, or no deal. So, if you just make the margin stated, you make money and the tree owner sees that they were not taken advantage of. This is analogous to a "log sale" in commercial logging. If you sell above your margin, they get some money as well. They also may want to stipulate what buyers to shop the logs to, if they know something about this end of the biz.
If you can just get a swap, removal for the wood, that is fine as well, but you may not get a lot of referrals --- which could be balanced by a windfall if it turns out you get top dollar for the wood. This is kind of analogous to a "lump sum" sale in commercial logging; in this case, your bid for removal is the lump sum. You owe the seller no documentation of what you sold the wood for. Would this be taking advantage of the tree owner (if you made a large profit) or just good hard nosed business? Up to you.