Lava zones decide insurability
The USGS lava hazard zone classification for the Big Island is the single most consequential fact about a parcel there. Zone 1 and Zone 2 land faces serious obstacles to insurance and, following from that, to mortgage financing.
Land in these zones is genuinely inexpensive, and for a cash buyer accepting the risk it can be a rational purchase. It is not a bargain in the sense of being underpriced — the market has priced the hazard accurately.
Check the zone before anything else, and get an insurance quote before assuming a purchase is financeable.
Fee simple versus leasehold
Leasehold tenure is common in Hawaii, and a leasehold interest is a fundamentally different asset from fee simple ownership. The value declines as the remaining term shortens, lease rent can reset on schedule, and at expiry the improvements may revert.
Confirm tenure explicitly on every listing. Where leasehold, read the lease: remaining term, rent reset provisions, renewal rights and reversion terms.
Agricultural zoning and residential use
A large share of Hawaii's land is zoned agricultural, and counties have become stricter about residential use that is not connected to genuine agricultural activity. Farm dwelling agreements and enforcement against non-farm residential use on ag land are live issues.
Before buying agricultural land intending to live on it, confirm with the county what is permitted and what obligations attach.
Water, access and utilities
County water is not available everywhere. Catchment systems are normal in many areas and entirely workable, but they are a different proposition from a municipal connection and affect financing on some parcels. Access on unpaved subdivision roads, common in Puna and elsewhere, affects both usability and insurance.
What to verify
Lava zone and insurability. Fee simple or leasehold, and lease terms if the latter. Agricultural zoning and permitted residential use. Water source and access condition. The risk scorecard screens the general fundamentals.