How do you quote scan-to-BIM before you've seen the site?

Quoting modelling from a scan before a site visit is one of the hardest parts of the job. Get it wrong one way and you lose the bid, the other way and you lose money.

Curious how people here do it:

• Do you price per square foot or square metre, per element, per hour, or per project?
• What do you ask the client for before quoting (drawings, photos, a sample scan, LOD per discipline)?
• How do you handle MEP-heavy areas like plant rooms, which can take several times longer than the rest of a building?
• Do you build a contingency in, or quote a range?

Share whatever you're comfortable with. Ranges and rules of thumb are more useful than exact numbers.