The chainsaw mill such as the Alaskan or others will make timbers and boards with a lot of work and a large kerf so a lot of waste, but has the advantage of machinery investment being relatively cheap. I bought a bandsaw used for $3500 that will cut 20' logs and up to appx 30" diameter. The kerf from most small bandsaws is 1/8" so there is very little waste. I can cut clapboard siding 1/2 inch thick or less if desired, accurately. It will also cut as large a beam as will fit under the carriage and can be extended to any length by buying or fabricating more track sections.
Occasionally there are cheap used mills here
http://www.sawmillexchange.com/
or ask around your local area if you are in timber country.
A bit more expensive but well worth it if you have a need for lots of lumber. :D
Glenn