The dispo guys keep telling me they don't do land

The fee difference tracks the buyer pool. A house dispo service can send one address to several hundred buyers who all want the same thing, a three bedroom in a price band, and get offers in a day. Rural land buyers are fragmented by use. Someone who wants 11 acres for a cabin site isn't the person who wants 4 acres for a manufactured home, and access, well and septic feasibility, and whatever the county allows on the parcel each cut the pool again. So the person quoting you 40% is pricing more calls per closing, not just a bigger appetite.

What you're buying at that price is the buyer relationships and the work of matching. Before agreeing, ask him how many land closings his buyers have taken in your county or an adjacent one, and what he does if nobody bites in three weeks. Percentage of spread with a flat floor is a common shape, so ask what the floor is, because on a $10,000 spread the floor may be the number that actually governs.

On the mechanics: your purchase contract has to permit assignment, and "and/or assigns" after your name is the usual way that gets handled. Whether your assignment fee is visible to the seller, and whether any written disclosure is required, depends on your state and sometimes on the title company's own practice, so read your contract and ask the closer in that state directly. Land closings also tend to surface title problems, old access easements and unreleased mineral or timber deeds, later in the process than house deals do, which is what usually kills a land assignment rather than the buyer disappearing.

Before you sign a 40% deal I'd want to know what stops him from taking your parcel, telling you nobody wants it, and coming back to the seller in sixty days when your contract has expired. Ask for a non-circumvention clause with a time period on it and ask whose name goes on the assignment. If he won't put either in writing, the 40% question is moot.

Rural land in most counties has four or five people who buy everything. Sign boards, the guy who bought the parcel next door, whoever the county assessor shows as owning six parcels under one LLC. That's a week of calling and it costs you postage. I wouldn't hand over 40% before doing that week.

I thought dispo meant the in-house salesperson at a wholesaling company, like a job title. So there are outside firms that do it for other people's deals on commission? That reframes a lot of what I've been reading.

If you're willing to carry paper on the 11 acres you're fishing in a totally different pool, and it's a bigger one for rural land. Buyers who can't get a bank loan on raw acreage will take terms. But that turns your assignment into a note sale question, and I don't think a house dispo service knows what to do with that at all.

Numbers, because nobody's put any in yet. Say the 4 acres is contracted at $28,000 and resells at $38,000. Spread is $10,000, his 40% is $4,000, you keep $6,000 less whatever the closer charges, and you've still got the earnest money at risk. At those absolute dollars I'd care more about his flat minimum than his percentage, since a $2,500 floor on a $10,000 spread is fine and a $5,000 floor is not.

The thing I was too embarrassed to ask for a long time: does the end buyer see what I'm making? On an assignment the fee generally appears on the settlement statement, so in practice the buyer often does see it, and in a good number of states sale prices aren't public record at all so the after-the-fact discovery is different again. I'd rather the buyer know up front than find out at the table and get annoyed.

Three documents worth having drafted before you're under time pressure, and I'd have an attorney in the state look at them: the assignment agreement itself, an addendum confirming the seller consented to assignment where your contract requires consent, and a short JV or fee agreement with the dispo person that says who holds the earnest money and when he gets paid. The last one is where the fights happen, because "40% of the spread" is ambiguous about whether costs come out first.