How to use it

1. Find the parcel. Take the parcel number from the sale list and search it in its city.
2. Compare the county's value with similar lots. A comparable is a vacant residential lot in the same neighborhood, or failing that the same city, half to double the size, sold on its own in the last 24 months for $1,000 or more.
3. Heed the warning. When the county's value is under a fifth of what similar lots fetch, the parcel may be a sliver, wetland or landlocked. Comparable sales may not apply.
4. Set your limit. Add your title clearing costs and choose the share of value you'll spend. The calculator gives your maximum bid.
5. Confirm it. Read the Property Appraiser's record and the tax deed file, and walk the land if you can.

Why bulk sales are left out

One deed can carry many parcels, and each parcel then shows the whole price. When two parcels share a sale date and a price, both are dropped from the comparisons, so a developer's bulk deal can't make a small lot look valuable.